UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN _. CIRCULATING COPY AGRICULTURE LIBRARY MAINTENANCE INSPECTIONS OF SIXTY FARM TRACTORS by J. A. Weber UNIVERSITY OF ILLINOIS BULLETIN 624 AORICULTURE LIBRARY JAN 2 1 1990 AGRICULTURAL EXPERIMENT: STATION CONTENTS PROCEDURE 3 TRACTOR INSPECTIONS 4 Method of Scoring 4 Condition and Grouping of Items. ... 6 TRACTOR REPAIRS 8 QUESTIONING OF THE TRACTOR OPERATOR 10 COMPARISON OF MANUAL RECOM- MENDATIONS AND OPERATORS' ACTUAL PRACTICES 13 MAINTENANCE OF INDIVIDUAL ITEMS. .16 Governor Adjustment 16 Crankcase Oil Condition 17 Oil Type and Viscosity 18 Brake Adjustment 19 Tire Pressure 19 Ignition Point Condition 21 Battery-Liquid Level 21 Carburetor Float Level . . . . 22 Air Cleaner Service 23 Valve Clearances 24 Crankcase Breathers 26 Transmission Oil Change 26 OPERATORS' MANUALS AND TRACTOR DESIGN 29 RECOMMENDATIONS 33 Standardizing Maintenance Intervals. 33 Making Recommendations Realistic. . .33 Improving Instruction Manuals 33 Fastening Metal Reminders on Tractors 34 Improving Communication Between Farmers and Manufacturers. . . . 34 SUMMARY 36 APPENDIX 37 Summary of Tractor Inspections 37 Summary of Operators' Answers to Personal Interview 40 LITERATURE CITED . . .44 ACKNOWLEDGMENTS This study covers one phase of a project on improvement of tractor main- tenance sponsored by the Illinois Farm Supply Company, which is provid- ing part of the financial support and the services of the laboratories of its Petroleum Division. A number of petroleum and machinery companies also gave valuable assistance in planning the tractor inspections and establishing methods of evaluation. Especial acknowledgment is made to senior mechanic Roy Brockett, whose careful tractor inspections and pleasant personal relations with the operators contributed greatly to the success of this study. Ultimately, of course, this report was dependent upon the cooperative spirit of the 60 farmers who made their tractors available and were tolerant in answering the many interview questions. Urbana, Illinois February, 1958 Publications in the Bulletin series report the results of investigations made or sponsored by the Experiment Station MAINTENANCE INSPECTIONS OF SIXTY FARM TRACTORS By J. A. WEBER, Assistant Professor of Agricultural Engineering FARM MACHINES are powered by millions of tractors. To farm efficiently, owners must keep their tractors operating at peak per- formance and extend the life of tractor parts. This goal can be accom- plished through proper tractor care and maintenance. Although bus and truck fleets are held to strict maintenance sched- ules, and even the private automobile is usually cared for by a service station attendant, the maintenance chores on the farm tractor must be performed by the owner or operator himself. Each owner must be made aware of the maintenance chores on his tractor and must be motivated to complete them, even though other farm activities and responsibilities may be demanding his time and attention. Several previous studies have shown the importance of performing these chores. Bateman and Weber tested 18 tractors "as found," and again after simple repair and adjustment. They reported an average increase of 16 percent in maximum power and 19 percent in efficiency as a result of performing maintenance chores (2)*. In a later study at the University of Nebraska, Smith and Larsen showed an average gain of 8 percent in power and 10 percent in efficiency (5). This report deals with the problem of obtaining better tractor maintenance on the farm. The 60 tractors in this study were inspected for evidence of good or poor maintenance practices rather than horse- power and efficiency. The condition of the tractor was then correlated with the operator's actual practices and his knowledge of manual recommendations. The condition of individual parts and interviews with the operators indicated several possible methods for improving tractor care, increas- ing operating efficiency, and extending the life of tractor parts. PROCEDURE The tractors included in this study were privately owned by farmers of Champaign county and surrounding counties. To qualify for inspec- tion, a tractor had to be one of ten specified models and at least two years old. A minimum of two years of ownership was considered * Numbers in parentheses refer to the literature citations on page 44. 4 BULLETIN NO. 624 [February, necessary in order for the inspection to reveal the operator's main- tenance habits. The Shell ADC Spot Test (1) was used to check oil condition; viscosity was checked by comparing the sample from the crankcase with known standards in the falling ball test. Engine timing was checked with a neon light. The degree of air cleaner restriction was measured by inserting a hypodermic needle in the air cleaner hose and measuring the air cleaner vacuum with a water manometer. During the tractor inspection, the operator was personally inter- viewed on three phases of tractor care: 1, his knowledge of the tractor manual recommendations; 2, his actual practice; and 3, his opinion as to what should be done. Operators were encouraged to answer as many questions as possible and to guess at the manual recommendation if they were uncertain of the answer. The tractor inspection and operator interview covered all items of "on the farm" maintenance. A list of the parts included in the inspec- tions and the items covered in the questionnaire is given in the Appendix. For ease in tabulating results, information from both the inspec- tion and questionnaire data sheets was placed on IBM punch cards. Analysis of variance procedures were used to determine significant differences in inspection results and life of tractor parts. TRACTOR INSPECTIONS Sixty tractors, representing ten models of eight different makes, were inspected in the summer and fall of 1955. Five of the tractors were Diesels and five were operated on liquefied petroleum gas. In this report, the models will be designated by letters A through J. The in- spection included 9 tractors of model A, 10 of model C, 6 of model H, and 5 tractors each of the remaining seven models. The number of tractors of each model inspected approximates the proportionate number of that model owned by farmers in Champaign county and adjoining areas. METHOD OF SCORING Seventy-eight points or items were included in the tractor inspec- tions. A tractor in perfect condition received a maintenance score of 78. The score was reduced by the number of maintenance deficiencies. For example, if ten items on a tractor showed lack of care, the main- tenance score for that particular tractor was 68. J958J MAINTENANCE OF SIXTY FARM TRACTORS 5 Each tractor included in the inspection, with its respective main- tenance score, is shown in Fig. 1. The ages of the operators ranged from 25 to 70 years, and no correlation existed between the operator's age and tractor condition. T 78.^ r^-MAXIMUM POSSIBLE SCORE 76 8 72 MAINTENANCE INSPECTION SCORE 64 60 56 5 52 4 u. , 48 o Q- 40 1, BB D G I AA B CC H B C AA I C G - C ODD E G A CC H F J MODELS Although scores often varied considerably for tractors of the same model, all of the tractors inspected had maintenance deficiencies. (Fig- 1) One model J tractor had the highest individual score (73 points), and all the tractors of model J had scores well above average. In in- terpreting these scores it should be remembered that model J was a Diesel, and the manual did not require operator service of its compres- sion ignition system. For this reason, model J automatically scored high on the condition of its ignition system. The spark ignition systems of the gasoline and LP gas tractors, on the other hand, were graded down if they were in poor condition. A model F tractor had the lowest score of all tractors inspected. Model F is operated primarily as a second or odd- job tractor in this area, and the odd-job tractor is often poorly cared for because it is used for jobs that do not demand peak power and efficiency. It is also difficult for operators to remember the maintenance intervals for tractors used on very irregular schedules. 6 BULLETIN NO. 624 [February, CONDITION AND GROUPING OF ITEMS For the inspection, the condition of individual items was either judged "o.k." or classified as having some degree of deficiency. For example, the battery liquid level was classified as "o.k.," "high," "low," or "below the plates." To compare the condition of all items inspected, each item was placed in one of three categories: in good condition; needed attention but getting by; and needed immediate attention. After all tractors had been inspected, the items were divided into three groups (Fig. 2). The grouping of the items was based upon the number of tractors with a deficiency and the importance of the item to tractor performance, life of parts, and operator safety. Group I: The items listed in Group I were either in good condition, or if not in good condition, did not seriously affect the performance of the tractor or the safety of the operator. For example, the PTO clutch adjustment was in good condition on 100 percent of the 57 tractors inspected. Battery charge, on the other hand, was satisfactory on only 79 percent of the 48 tractors inspected; it needed attention on 13 percent and immediate attention on 8 percent of the tractors. Since low battery charge is not critical to operation, however, this item also appears in Group I. Only a few of the items in Group I were in need of immediate service. Group II: The items listed in Group II could have been better cared for, but their poor condition was not a critical matter. For example, the rear axle splines on 34 of 46 tractors were rusty. This condition might make it difficult to adjust rear wheel width, but it would not affect operation in the field. Crankcase oil levels were low on several tractors, but the operators indicated that the oil levels would have been checked and oil added before the tractors started another full day of operation. Group III: The items in Group III were the critical maintenance items for these 60 tractors and definitely should have received better care. With a few exceptions, the deficiencies listed were found on all makes and models. (Poor governor adjustment was found on only two models; one model required no crankcase breather service; and, of course, Diesel engines had no spark ignition system deficiencies.) The proper care of the items in Group III concerns all farmers, agriculture extension workers, and the entire tractor industry. The condition of these items and the probable reasons for their neglect will be discussed in detail later in this report. 7958J MAINTENANCE OF SIXTY FARM TRACTORS ITEMS IN GOOD CONDITION NEEDED ATTEN- TION BUT GETTING BY NEEDED IMMED- IATE ATTENTION NO. OF TRAC- PERCENT OF TRACTORS INSPECTED TORS GROUP 1 2? 5,0 7,5 2^ 5,0 7,5 2^ 5,0 7,5 WATER TEMPERATURE -GAGE ^""i 1 52 SPARK PLUGS- RANGE E"""*"*"""""l 1 55 GENERATOR AND REGULATOR ! | 60 RADIATOR PRESSURE CAP ^l 1 60 POWER LIFT- HOSES AND GASKETS ^l 1 56 FRONT WHEEL BEARING - LUBR. ^i 1 52 OIL PRESSURE AND GAGE ^i 1 | 60 SPARK PLUGS - DEPOSITS ^1 55 SPARK PLUG WIRES ^i 1 1 55 SPARK PLUGS -CONDITION pBJJJJJJJ*a j 55 REAR TIRES -CONDITION > 60 CARBURETOR-MAIN JET-ADJUSTMENT fraaaaaaaaaaal 49 STARTER -OPERATION ^1 60 AIR CLEANER HOSE I 1 50 DISTRIBUTOR CAP ^""""i m 1 50 RADIATOR SCREEN * 45 CLUTCH -ADJUSTMENT ! M 1 60 BATTERY -CHARGE ^l 48 ENGINE-TIMING ^ 1 54 GROUP II 1 1 1 i i i FUEL LINES ^i j 60 RADIATOR WATER-LEVEL " IB 60 RADIATOR HOSES ^l M 60 AIR PRECLEANER- SERVICE N""*"""""" ) 1 59 TRANSMISSION OIL- LEVEL f"*"*""* ^ l 60 FRONT WHEEL BEARINGS -AD JMT. [1 JJJf 57 FRONT TIRES -CONDITION ^i LBBM I 60 AIR CLEANER-LEVEL 1 1 59 CARBURETOR IDLE-ADJUSTMENT 50 BREAKER CAM -CONDITION ^^^ ^^ 1 48 FAN BELT -TENSION jjjjjjjj JJJJJJJ 55 CRANKCASE OIL-LEVEL OVBBBI i 59 POWER LIFT OIL-LEVEL ^B 50 STEERING GEAR-ADJUSTMENT HHHHH BBHBHBI 1 BATTERY-CLEANLINESS "*" ^^^ 1 60 RADIATOR FINS- CLEANLINESS jjjjjj JJJJJJJJJ 60 SPARK PLUGS -GAP jjjjj i 55 TRACTOR-CLEANLINESS h"""""""""* 60 REAR AXLE SPLINE-CONDITION h^ 46 SEDIMENT BOWL- SERVICE . 1 47 GROUP III i i i i i i ' ' ' GOVERNOR - ADJUSTMENT JJJJJJJJH HJ| JJ| 60 CRANKCASE OIL -CONDITION IHHBHH B 59 BRAKES -ADJUSTMENT IHBBBBBl | 60 REAR TIRES -PRESSURE jjjjjBI IHHi 60 IGNITION POINTS -GAP ^"" 47 BATTERY- LIQUID LEVEL JJJPJJJPJI HJJJ jjjj 60 CARBURETOR FLOAT- LEVEL J IHHHi 50 AIR CLEANER BODY-SERVICE Ml HHHHiB 58 IGNITION POINTS -CONDITION ! 50 EXHAUST VALVES -CLEARANCE ^ 55 INTAKE VALVES -CLEARANCE JJJJI BBBBjjjl jj| 55 FRONT TIRES-PRESSURE i H| B^HMHBHI 60 AIR CLEANER CUP-SERVICE n ^H Mi 60 CRANKCASE BREATHER -SERVICE "" ^~ " 54 The condition of all items inspected needed improvement, but the items listed in Group III are critical to tractor operation and should be considered first in a maintenance improvement program. (Fig. 2) BULLETIN NO. 624 TRACTOR REPAIRS [February, Operators of the 60 tractors were asked to look up in their records or attempt to recall the type and number of repairs that had been made to their tractors. The average frequency of repairs or replacements of various tractor parts is shown in Table 1. The first column shows the number of tractors with one or more repairs or replacements of a given item. For example, 53 tractor owners reported one or more spark plug set replacements, and the average plug life on these 53 tractors was 1.3 years. Many of the expensive tractor parts, such as rings, pistons and sleeves, tires, etc., have an average life of four to five years; and as previous studies have shown, the tractor owner usually can expect a large repair bill during the fourth or fifth year of operation. Analysis of variance was used to determine the differences between models in the life of parts. Those parts for which a significant differ- Table 1. Life of Parts of 60 Farm Tractors Items Number of tractors Years between repairs Average interval Shortest individual interval Longest individual interval Spark plugs, replaced 53 1.3 2.8 3.2 2.5 2.8 4.7 4.1 4.5 4.6 3.6 5.4 6.0 3.9 4.0 4.2 4.6 5.5 5.4 2.0 4.5 .5 1 1 1 .7 1 1 2 3 1 2 4 2 2 1 3 3 3 2 2 6 5 8 7 7 8* 8* 8* 8 8* 8* 9* 5* 6* 7* 7* 9* 7* 2* 7* Battery, replaced 50 Valves overhauled 35 Fan belt, replaced . . 34 Magneto or distributor, repaired . Pistons and sleeves, replaced 24 . 24 Piston rings, replaced 24 Front tire, replaced . . 22 Rear tire replaced 20 Generator, repaired . . 17 Brake lining, replaced . . 17 Governor, repaired . . 12 Clutch, relined 12 Carburetor, repaired 10 Hydraulic systems, repaired 9 Steering gear, repaired 8 Front wheel bearing, repaired .... 7 Transmission, overhauled 5 Water pump, replaced 2 Starter, repaired ... 2 * This item had not been repaired on some tractors 10 years old at the time of inspec- tion. The average age of all tractors inspected was 5.7 years. 7958J MAINTENANCE OF SIXTY FARM TRACTORS ence in life was found between tractor models are listed in Table 2. Because of the small number of tractors involved in this study, it could not be determined if there was a significant difference between models in the life of the other parts in Table 1. Only the models with the shortest and longest intervals between replacements or repairs are listed in Table 2. For example, the average life of spark plugs was shortest (0.9 year) in Model A and longest (4 years) in Model I, an LP gas tractor. Table 2. Life of Parts That Differed Significantly Between Tractor Models Years between re pairs Item Average Shortest interval Longest interval for all tractors Tractor model Average interval Tractor model Average interval Spark plugs, replaced . 1.3 A .9 I a 4.0 Battery, replaced (original only) ... 3 4 A 2 8 c 3 9 Battery, replaced (all) 2 8 A, E, F 2 3 c 3 1 Valves (first overhaul only) . Valves (all overhauls) . 3.9 3.2 B B 1.8 1.7 E E 5.5 4.6 Piston rings, replaced . 4.1 B 2.5 I (not Piston and sleeves, replaced . Fan belt, replaced . 4.7 2 5 A A 4.0 2 3 I C needed ) b (not needed) b 3 2 a Model I is an LP gas tractor. b No overhauls in an average of 6 years of operation. Although plug life varied significantly between gasoline and LP gas tractors, there was little variation among gasoline tractors. Gaso- line tractors varied widely, however, in life of both original and re- placement batteries. In valve life, Model B differed considerably from other models. In piston rings and pistons and sleeves, as in plug life, the significant difference was between gasoline and LP gas tractors rather than among the gasoline models. Fan belt life varied from 2.3 years for Model A to 3.2 years for Model C. The life of some tractor parts apparently varies more from model to model than between tractors of the same model. But by sound main- tenance practices, the farmer can extend the life of the parts of his tractor to exceed the average for his particular model. 10 BULLETIN NO. 624 [February, QUESTIONING OF THE TRACTOR OPERATOR Each of the 60 tractor operators was interviewed on three aspects of tractor maintenance: 1. His actual maintenance practice for each item on his tractor. 2. His knowledge of the frequency of service recommended by the manual. 3. His opinion as to the amount of service each item should receive. Operators were asked to describe their own practice during the busy season when the tractor was used every day, and to answer as many questions as possible about the manual recommendations (even guessing if they were not sure). Practically all of the operators gave definite answers about their actual practices, but several did not answer the questions on manual recommendations. Although all 60 operators were asked to answer all of the questions, only those operators whose manuals had a specific recommendation are included in the analysis in Tables 3, 4, and 5. For example, since only 25 of the 60 operators had manuals with a recommended interval for inspection of distributor points, only the answers of these 25 operators are included in the three tables. The operators' answers were compared with manual recommenda- tions. Since the recommended interval of service varied from item to item, and from tractor to tractor for the same item, the comparison with manual recommendations could not be summarized until the answers were placed in five classifications: 1. The answer agreed with the manual recommendation. 2. The interval of service given in the answer disagreed as much as 100 percent from the manual recommendation. For example, if the recommendation was once a week and the answer was once every two weeks, it would appear in this classification. 3. The answer disagreed with the recommended interval by more than 100 percent. 4. The operator said that the item was never serviced. 5. The operator did not answer the question, or his answer could not be classified. 7958J MAINTENANCE OF SIXTY FARM TRACTORS 11 i| i CS -H CN O-J "H *s > Service n Q a Sle 1 5 I V itions as to Frequency c rcent of operators questione< lil V .3 n .2 >- A 3 o i* C "3 >% 'S VM Jecommend. 111 I O C r* ;ommendations ractices Related to Manual I Number of Foil operators ma recori dat ! 1 r * O ^x ^^ ^5 l/^ ^5 W^ ^D ^5 ^^ ^J "3 ^O ^D ^^ ^^ ^* C ^2 ^^ ^"^ ^^ OC C ^^ C^ ^^ "> *~* tw *O O ^O ^O cs 10 ^O ^O ^O ^^ f^ *O r^ ^^ 10 'O ^O V O ^* *^* ^* f5 ^* *O ^O C^ ^* C*^ operators were following manual re< ations satisfactorily. & 1 < e 2 ators' compliance itions) :::::: :::::: :ms for which the manual recommenc 0) c. 1 co 3 & Items (Listed in order of oper with manual recommend; s^lil iliil &| : . sill? ililllils ^lifllflliHi !i Si III! SUP 00 c fi ~ o *: n > ' 2 a h V a. o 12 BULLETIN NO. 624 [February, C* c 5 "3 o Sit rs.i Off more han 100% al n erv Yin off Q" Knew ecommen dation exactly 2* 1 M-l 5 o S ,. P (Listed i with man OO"O CNrocNOfO -LO^CI ^-H CM > CN (TJ OO CN ir> OO CN o o t *O vo 1 1000 o ^ LO O VO O Tt \O vO i 4-> : : : : : 0) . . . 56 c . 41 - 4) ; : ; 03 . .y '^ cd 4> . 4) . QJ J^ C M r3 be cj ' O C 4) o3 03 u e :.2 ! '42 U 4) 4-1 4) bX) rt 43 , J! ^ ] -= o 41 O U c ' a e aon ica mple C C ^ o3 S . . ' ,., i. S 2' JiHS rt 03- 'C i ug .S'S-S-c rvr~ *^ "-Ij frt *-* o ; -j- u u c.o^ o ^ nj *^ ^O i_ ; 53 41 g, ^ v-2. o fc | c-a ^ ^ ^-2^ c !l!.S ^^fe.-2^ )fi U ^.-H^jUir) ' w "^ - *" L- 4_) ^^ ^ 2 03 .2 u U U c/5 Q < nsmission oil c tch adjustmen pressure chec ke adjustment a e T Clu Ti Br 7958J MAINTENANCE OF SIXTY FARM TRACTORS 13 COMPARISON OF MANUAL RECOMMENDATIONS AND OPERATORS' ACTUAL PRACTICES In Table 3 the maintenance items are listed according to the per- centage of operators who were following the manual recommendation. For example, practically all of the operators were either checking engine oil level according to manual recommendations or at intervals less than 100 percent from manual recommendations. By contrast, most operators checked tire pressure and brake adjustment at intervals varying more than 100 percent from manual recommendations. For convenience in discussing these maintenance items, they are divided into two groups X and Y. Operators were doing a fairly good job of following manual recommendations for the items in Group X, but not for the items in Group Y. There was no apparent correlation between the condition of an item and the operator's compliance with the manual recommendation. For example, operators complied closely with recommendations for battery level check, distributor points inspection, and engine oil change (listed in Group X). Nevertheless, the battery level, points, and engine oil were often unsatisfactory. Other critical maintenance items in poor condition air cleaner, crankcase breather, tire pressure, and brake adjustment appear in Group Y. More than 50 percent of the operators having manuals with spe- cific recommendations never change oil in the steering gear, transmis- sion, or power lift, or completely clean the air cleaner. Between 25 and 50 percent never check valve clearances, lubricate the distributor, or service the crankcase breather. OPERATORS' KNOWLEDGE OF MANUAL RECOMMENDATIONS The operators' knowledge of the manuals is shown in Table 4. The maintenance items are listed in the same order as in Table 3; that is, in order of the percentage of farmers who were actually following manual recommendations. Again, the number of operators who owned manuals with specific recommendations is given in the column headed "number of operators." Those operators who did not volunteer an answer as to what the manual recommended are listed in the "did not answer" column under "percent of operators questioned." Sixteen farmers (27 percent of the 60 operators interviewed) did not believe that they knew any of the manual recommendations and would not attempt to answer this part of the questionnaire; yet all of these operators were following some type of recommendation in their 14 BULLETIN NO. 624 [February, fc c ^ e*} ro CN vO ro CO t^> CN uo O ^O u"> T-H ro t^. OO ^ ^- OO ON OO O ^~ CN O TO to m c*5 T-H CN CN T I CN T-I T^< CNCN CO ^f CN CN T I CN Q rt M O _C 4) C 4> 4) o JJ & CN IO T I rC rf) C H -^ V) CN t^* T-H ^O CN OO t^* LO (O *^f t*^ 1^* ^^ t^* . 1^ CO V O CO f3 i^* CN to f* CN OO O 1 T < T^ CN T-H T-H CN CN CN CN T-H T-H T+< T^H r/} . ^4< \o CO T-H ro T-H t~- V O 1 O he d 4) 0.2 -S O ** O E ^S "^3 4> P O en Ui t^* 1^5 ^O CN CO ^O ro OO W) CO ^""3 T+< ON -^ IO t~^ OO C^5 CN I/"} CN CN t"* ro CN OO W> (^ 4) rOCNT-HCNCN CNT-HrOT-HC-Oir>CNT+< T I CN CN -^ T-H T-H T I T-H T-H OH aa ^ c o- -C , s- < ill OOIO< S OCN'O Ol^^OOrtl CNO-HON Tfm"^r<)lO trjlOCNlOlO "5 l~" l/OlO-'flOC*} ^ ^f ^* f> f*b CNCN-^CN CN CN CN T IT I T-HCNf-OT icN T ~ < < 2 X ^ 0* ^ O tn ^ ^ u, o Orj OOOO*O OOOOO OO^*-* O O O O ^ ' OOOOOO O iO ^ i O \O *O 10 ^O rN 10 ^O ^O ^O ^" ro ^'C ro "^ *-O ^O ^O ^O ^f ^^ ^^ r*o ^^ 'O *O CN ^^ CN 3 a V s o *_ c/3 " S o - . . b/) . . . . '5 a, .... ; . . C .... : "' S-^^"~ t -^o u -o M u 5 S -n S rt ajrt^cj-^ CJ^-^> i y OcajrtS h - J3 *j J< -s-sj^- ^^^s= & E^-S-S^ l|f-ij = llill SfifSl'S BJl-a t^g-'S s^sls Sfisi "* >l c3 ^-5- S g^'Sj ^ ^ S StS S b WS 3 s^- 2 "! iSSsSi'glt .sss|Slil|s Ifi's 1 4.0.^2^ ^^c^4. a 2 gSS^c xlfe^g ej? rt S.SS.S'c a; s s trc ae s-.2 s-s-S-yc o-^^'c-S s^ a _s aCbfilj'C 4 ^ ti S5 n? 5 i! ^'aC^'O "O S W tiM u4 ^ S IS P*3 r-Tr-^'t;;;; 1 ' 3 rtr'r^ricu'^r-^^M >,ucuOa> SrttH^u ro3u.,~ C G Cu TO >-^ M tH W J*\ rt C CZLi tv ^". . l-i 4.J ~ U< ^j -^ . VH -. . -~ I-H W W p3 OH Q |> O O O c/) ^> W t/3 OH ffi*:: 6 ABCDEFGHIJ 12 NO ANSWER 48 WHAT THEY THOUGHT SHOULD BE DONE WHEN LOOKS LOW ** 23 4-6 MONTHS 6 2 MONTHS 1 1 MONTH 5 2 WEEKS 2 1 WEEK OR 60 HR. :*' :'-*:' 7 ABCDEFGHIJ 44 NO ANSWER 16 Few operators used a gage to check tire pressure. As a result, rear tire pressures were too low. (Fig. 5) J958J MAINTENANCE OF SIXTY FARM TRACTORS 21 IGNITION POINT CONDITION Ignition points were found to be excessively pitted on 27 of the 55 tractors with ignition systems. Point gap was correct on 27 tractors, too large on 4, and too close on 17. Of the 17 tractors with point gaps that were too small, 13 had pitted points. All tractors with dirty or dry cams had pitted points, indicating that wear of the ignition point fiber block and closing of the point gap may be a major cause of point pitting. Only four of nine tractor manuals recommended an interval for ignition point inspection. These recommendations varied from 200 to 700 hours. One manual had conflicting recommendations. Thirteen op- erators inspected ignition points yearly, 9 twice a year, and others inspected points only "when needed" or not at all. All tractor manuals should not only include a standardized interval for point inspection, but should also stress the importance of good igni- tion point condition. Longer point life could undoubtedly be achieved if the breaker cam received proper lubrication. BATTERY LIQUID LEVEL The battery liquid level was low on 27 of the 60 tractors. On 16 of these tractors the liquid level was below the top of the plates. Twelve of the 16 also had corroded terminals. Models A, F, and I each had three batteries with the liquid level below the plates, and models A and F had significantly shorter battery life than the other models. Manual recommendations for interval of battery inspection varied from a week to a month (Fig. 6). One manual listed three different intervals. Despite the diversity of recommendations, operators were following them fairly well. But only half of the 26 operators who volunteered knowledge of the manual actually knew the recommenda- tions for their tractors. Ten of the operators who said that they were following manual recommendations had batteries with the liquid level below the plates. No relationship existed between frequency of battery service and the battery's liquid level at the time of inspection. This fact might indicate that each battery and electrical system had its own required frequency for adding water. If it is impossible to reach a standardized recommendation for all tractors, then the individual recommendation must be spelled out clearly, and conflicting recommendations should never appear in the same manual. Importance of maintaining the liquid level above the plates should also be stressed. Thirty-three of the 60 operators were using well water in their tractor batteries. The type of water used apparently had no significant effect on battery life. 22 BULLETIN NO. 624 [February, FREQUENCY OF BATTERY LIQUID LEVEL CHECKS ON 60 FARM TRACTORS FARMERS' RESPONSE TO QUESTIONS : : ;:; MANUAL RECOMMENDATIONS WHAT F 3 TO 6 MONTHS 2 MONTHS 1 MONTH 2 WEEKS OR 120 HR. 1 WEEK OR 60 HR. TWICE A WEEK ARM iMi EPS DID 0*W o NUMBER 6 21 8 24 1 : ':':' :*: ABCDEFGHIJ 60 NO ANSWER WHAT T 3 MONTHS 2 MONTHS 1 MONTH 2 WEEKS OR 120 HR. 1 WEEK OR 60 HR. TWICE A WEEK HEY THO UGH! r TH E Mt \NUA L Rf :cov MEN :': DED 1 6 16 3 |:*:| *fi*:! ''*.'' '+ :: ABCDEFGHIJ 26 NO ANSWER 34 WHAT T 3 TO 6 MONTHS 2 MONTHS 1 MONTH 2 WEEKS OR 120 HR. 1 WEEK OR 60 HR. TWICE A WEEK HEY THO UGH7 SHC )ULD BE DON E W:' ** 4 19 7 26 4 ::: : ABCDEFGHIJ 60 NO ANSWER Although operators followed manual recommendations fairly well, the bat- tery liquid level was low on 27 tractors. (Fig. 6) CARBURETOR FLOAT LEVEL Eleven of the 50 tractors with carburetors had poor float level ad- justments. Four of the 8 tractors with float levels }4 inch too high were of tractor model G. All 3 of the tractors with float levels }4 inch too low were of tractor model E. 1958J MAINTENANCE OF SIXTY FARM TRACTORS 23 Since the operator is not responsible for adjusting the float level, this adjustment should be checked during the dealer's tuneup and when a mechanic is "trouble shooting" on a tractor with poor performance. AIR CLEANER SERVICE Service of air cleaner cup. Forty-six of the 60 tractors had more than }4 inch of dirt in the air cleaner cup. Seventeen of these tractors had more than 1/2 inch of dirt. Although 39 operators said that the manual recommended daily service of the air cleaner, only 9 operators were actually following this practice. The largest group believed that twice-a-week inspection and change of oil was sufficient. Daily air cleaner service takes about 480 minutes a year, or about 13 percent of the total time required for on-the-farm tractor main- tenance (Table 7, pages 30-31). All but one manual recommended daily inspection and change of the air cleaner oil; yet only 23 operators changed oil oftener than once a week. The oil level in 2 cleaners was more than 1/3 inch low. In 19 others the level was 14 to 1/2 inch low. Compliance with recommendations is much better when these rec- ommendations are realistic. To make the air cleaner cup recommenda- tion more realistic, it is suggested that manufacturers continue to recommend daily inspection but recommend oil change only when the dirt has accumulated to a certain depth or the oil has thickened. The operator will not take the time or use the oil necessary for daily service if he finds that he is throwing away oil from a clean cup. Some method of checking the cup without removing it would allow quick daily inspection. Manufacturers are now testing transparent plastic air cleaner cups. Dry-type air filters, which are also being field-tested, are easier to service than ordinary oil bath cleaners, but may require as much total service time because of a limited capacity for dirt. Service of air cleaner body. Air cleaner vacuum or amount of restriction was found by measuring the pressure between the air cleaner and carburetor with a water manometer. The manometer readings showed that most gasoline engines containing throttle plates have less than 3 inches of water vacuum at full-throttle no-load when the air cleaners are kept clean. Diesels have considerably higher readings be- cause air flow is not restricted by a throttle plate. The manometer readings for gasoline tractors with restrictions were as high as 8 inches at full-throttle no-load. Seven of the 60 air cleaners were excessively restricting the flow of incoming air, and 5 of these 7 restricted air cleaners were found on models A and F. Restriction was 24 BULLETIN NO. 624 [February, caused by dirt in the cleaner body. A visual inspection of the bottom of the air cleaner elements proved inadequate; upon inspection, 2 of the 7 restricted air cleaners appeared to be clean. Manual recommendations for complete cleaning of the air cleaner varied from 60 hours to once a year. The state of operator education on these recommendations was very poor. Thirty-six operators had no idea of what the recommendation might be. Thirty-five of the 60 oper- ators said that they had never removed the air cleaner or given it a complete cleaning. Operators of 6 of the 7 tractors with restricted air cleaners were in this group. If all manufacturers would adopt a standardized service interval of one year for cleaning the air cleaner body, it would be easier to con- vince farmers of the importance of this maintenance chore. It should be possible to design the air cleaner so that it can be completely cleaned without removing it from the tractor. VALVE CLEARANCES On most tractors the clearances on both the intake and exhaust valves were greater than those specified by the manual. For example, the intake valve on the No. 1 cylinder had too large a clearance on 20 of 55 tractors and too small a clearance on only 7. The exhaust valve on the No. 1 cylinder had too large a clearance on 28 of 55 tractors and too small a clearance on only 8. This apparent tendency of valve clearances to increase with tractor use agrees with results obtained in a controlled study of valve clear- ances on 60 tractors (6). However, Smith and Larsen (5) found that the tractors in their study had less than specified valve clearance at the time of inspection. In six of ten manuals, recommendations on frequency of valve clearance checks varied from 250 to 400 hours (Fig. 7). Other manuals recommended adjustment "periodically" and "occasionally," or in- structed the operator to "maintain clearance." Only 16 of 60 operators volunteered answers on recommended frequency of valve clearance checks. The operators' actual practices diverged widely from manual recommendations, with 20 of the 60 operators either adjusting the valves only "when they were noisy" or neglecting them completely. Since mechanics often use larger than specified clearance in an attempt to prevent valve trouble, some operators were doubtful about the amount of clearance to use. If a manufacturer changes the recom- mendation for valve clearance from that specified in the manual, this 7958J MAINTENANCE OF SIXTY FARM TRACTORS 25 information should be distributed to all owners of that particular model tractor. Valve adjustment requires precision, and it is difficult for an un- trained person to perform this chore correctly. But if recommendations could be standarized to once-a-year intervals, valve adjustment could be made a part of the dealer's yearly tuneup. FREQUENCY OF VALVE CLEARANCE CHECKS ON 60 FARM TRACTORS FARMERS' RESPONSE TO QUESTIONS ::'.- MANUAL RECOMMENDATIONS WHAT FARMERS DID NUMBER NEVER 14 WHEN NOISY 2YR.OR MORE YEARLY *' | 6 10 9 .. 400-500 HR. :'*':'': *: = 10 200-300 HR. ':':' :;:: 3 ABCDEFGHIJ 52 NO ANSWER 8 WHAT THEY THOUGHT THE MANUAL RECOMMENDED NEVER 2 WHEN NOISY 2 YR. OR MORE YEARLY 400-500 HR. 200-300 HR. - ..'... M:. . T 4 7 3 ABCDEFGHI J 16 NO ANSWER 44 WHAT THEY THOUGHT SHOULD BE DONE NEVER 2 WHEN NOISY 3 2 YR. OR MORE 4 YEARLY :::-. 8 400-500 HR. **: * 16 200-300 HR. :':*: 7 ABCDEFGHIJ 40 NO ANSWER 20 Operators' knowledge of manual recommendations was poor, and their actual practices varied widely from these recommendations. (Fig- 7) 26 BULLETIN NO. 624 [February, Hydraulic lifters would eliminate the need for valve clearance ad- justment. One requirement for hydraulic lifters is the use of detergent oil. The fact that 45 of the 51 operators interviewed were already using detergent oil suggests that the switchover to oil for hydraulic lifters would probably not be difficult. CRANKCASE BREATHERS Crankcase breathers had the poorest maintenance record of the tractor items inspected. Thirty-two of 54 breathers were dirty, and 12 of these were apparently plugged with dirt. Operators' manual recommendations varied in frequency of service from "daily" to "no service required"; the term "periodic" was used in one manual. Thirty- four of 48 operators were unable to volunteer an answer as to the frequency of service required, and several were not aware that their tractors had a crankcase breather. One tractor manufacturer has eliminated crankcase breather main- tenance, and it would be desirable if all tractor manufacturers could follow his example. The value of designing construction machinery for ease of maintenance was stressed by Navarin and Usow (3). The same principle applies to farm tractors. TRANSMISSION OIL CHANGE Although transmission oil change is not considered a critical main- tenance chore, it illustrates a relationship between state of operator education and actual practice that should be considered when making up any manual recommendation. Thirty-nine of 59 operators never changed transmission oil. Most operators who answered the question (29 of 37) knew the recommen- dation of six months or one year, but only 15 of 44 operators thought it necessary to change oil as often as once a year (Fig. 8). The transmissions of 5 of the 60 tractors inspected had been over- hauled; yet the operators of 2 of these tractors were changing trans- mission oil at the recommended one-year interval. The frequency with which the 60 operators changed transmission oil had no apparent rela- tionship to their transmission system difficulties. Transmission oil change is expensive, messy, and time-consuming, and even the operators who knew the recommendation preferred to take the risk involved in disregarding it. The recommendation for transmission oil change illustrates the need for carefully examining each tractor maintenance recommendation. 7958J MAINTENANCE OF SIXTY FARM TRACTORS 27 Any recommendation that is not completely realistic or has a higher frequency than necessary will probably not only be disregarded, but will also detract from the appreciation of the importance of other mainte- nance chores. FREQUENCY OF TRANSMISSION OIL CHANGE ON 60 FARM TRACTORS FARMERS' RESPONSE TO QUESTIONS : : : : :i MANUAL RECOMMENDATIONS WHAT FARMERS DID NUMBER NEVER ... 39 5-6 YEARS e 3 3-4 YEARS 7 2 YEARS 3 1 YEAR 6 MONTHS *** !:*:! :::: 5 2 ::- :: A B C D E F G H 1 J NO ANSWER 59 1 WHAT THEY THOUGHT THE MANUAL RECOMMENDED NEVER 3 5-6 YEARS 1 3-4 YEARS 2 YEARS . . 4 1 YEAR 6 MONTHS 09. :*:: :*: = : :*> '*:': ... 18 II . ... .- ABCDEFGHIJ 37 NO ANSWER 23 WHAT THEY THOUGHT SHOULD BE DONE NEVER ... .*% . 18 5-6 YEARS . 2 3-4 YEARS 5 2 YEARS . . 4 1 YEAR 6 MONTHS .V. ** :*:: ''*''' :*.: .V. ::*>: 14 1 A B C D E F G H 1 J NO ANSWER 44 16 Twenty operators knew the manual recommendation, but only four of these operators were actually following it. Thirty-nine operators never changed transmission oil. (Fii- 8) 28 BULLETIN NO. 624 [February, 11 E" ^ ' 1 p 1 - 1 1 1 E >o" '?* i c O -"faE" .O" ^""fa" 4> in a> 5 O ^ "*- -.""". 8) "4J 9-5'.D _ _ ^il CQ O * [ T I ' rf] 3 13 > o n3 fa fa fa^ O -O T3 T3 T3 W rH\ pBri in 41 41 in 4) 4> 41 in -M (/3 [ft *O <-!--' to in <- l - "w Ui O 4-1 2 ,^_ x in o3 41 4> > bO CC C .5 4> _x _>, _> 5 g ^ "- O " U 2 o -*- 3 oS O '3 >, "3 '3 h b - 3 '5 cr-2 crSa" 22cr a ^ J3 ^^S^B^SBw^iS U-r-tiVT 1- i i U J3J- 1-,-r- 1-, M 2 M M <^J VH Ui M o3 o 03 oS-t-JO-t- 1 oSOO-M oS-u 3 ^ j= 41 "uO fe oSO M *S OJ rvj . ro 03 U *-H C>,g>,>>C^C>,^^C>,C C*$ ^t^H o "a3 T5 Q~i-rQ~i-C ouf OK-, WE" M u in * fc ^ T3 S 2"3 U E U E U W Q i, Wo" W Q o" tJ (U JO U o 03 o H E Q u 3 ^fa E" Q~fa" fa Q"U" fa" Q paooaocc "w oS c < fa < fa"< o O u pa O pa'E fa < O E pa u"pa pa O 42 ., , bfi "co ^w o ~ in C oS X >< tn * f 01 03 OJ ^ CO ja c/) (rt 'c3 2 -C en 2 ^ o ^ ^in * ^ 3 3 333 " ^ 15 S g > u "^ O ^ _>^ ^^ "c 3 O O -^js j2 J2 c ^ C fe flj _y "^ r^ ^5 f~] ' ^ ^* ^vo *~ *^ \^ ^ y j^jn 5? fll "- 1 c OJ C *"" C cti ^^ MD "oS 't5 T3 rt cb ^ c^ ^^ rt rt ^^ ^^ ^D ^^ *o ^ ^ o o o s ~ CO Q pa H-.HH faQ tTQ" Q" V -a d s H E < fa"E E o (j 2" 4) C O o u O "U O E ::.:: M 'S Q* 2-2 41 '-3 bfi -.5 CO -" rj rs _e oS ' ' C 41 C ' j.^'-'SoS*''" 1 u CO 1 &1 ill o S M , o 11 h u J^' -^' u o ^ 5 4> c 42 J3 4, o u j: 1 a o C ^.C os . C bfl 03 41 +-> iJ'"3 W-yO S 5 oS^" tn ^ "3 V "rt j.td .h c .= e C 41 C >-?* t^ o3 oS i **~t ^, .^ . Q^ ^ o3 *"^ .i- ^ j_ &$ < W P< < WH ow O >faP3Pi(y3UEUQ 7958J MAINTENANCE OF SIXTY FARM TRACTORS 29 OPERATORS' MANUALS AND TRACTOR DESIGN The manual recommendations for the ten models used in this study appear in Table 6. These recommendations are listed in descending order of the operators' knowledge of them. In determining this order, both the number of operators who gave the correct answer and the number who gave no answer at all were considered. Only those operators having manuals with specific recommendations were included. Since 65 percent of the operators gave the correct answer of "daily service" for the air cleaner cup, this item is listed first in Table 6. Brake adjustment appears last in Table 6 because only 5 percent of the operators with manuals giving a recommendation for brake adjustment knew the recommendation. Two factors appear to influence the state of operator education on any particular item : 1. The degree of standardization of the recommendation among tractor models. 2. The number of manuals containing a specific recommendation on frequency of service. For example, all ten manuals recommended daily inspection of the air cleaner cup. Since the recommendation is standardized, all informa- tion disseminated on this subject by manufacturers, fuel companies, and extension workers is in agreement, and the result is a satisfactory state of education among tractor operators. For crankcase breather check, on the other hand, recommendations vary from "daily" to "no service required" and operator education is poor. Operator education was high for the items listed in the first part of Table 6, and all ten manuals recommended a definite service interval for most of these items. In contrast, only four, five, or six of the ten manuals contained recommendations for many of the items in the latter part of Table 6. As a result, even those operators who had manuals with recommendations did not know these recommendations. About 60 hours a year, or 10 percent of the yearly tractor operating time, is required to follow manual recommendations to the letter. For a breakdown of the estimated time required for lubrication and mainte- nance of tractor model C, see Table 7. Analysis of other manuals gave similar results. Comparison of the manual recommendations and the actual prac- tices of these 60 operators (Table 3) shows that they spent much less than 60 hours per year on tractor maintenance. A previous study by R. I. Shawl (4) revealed that one owner averaged 33 hours of main- tenance chore time per year for 18 years. Since farmers are spending 30 BULLETIN NO. 624 [February, Table 7. Estimated Time Required for One Year's Lubrication and Maintenance of Tractor Model C (The schedule in this table was taken directly from the operator's manual for tractor model C. It is based on 600 hours of operation per year.) Services Minutes required per service Number of services per year Total minutes re- quired Daily or 10 Hours Air cleaner oil cup, inspect and change 8 60 480 Engine oil level, check and add 3 60 180 Radiator level, check and fill 2 60 120 Air cleaner cap, check and clean 1 60 60 Grease fittings: Water pump shaft 1 60 60 Rear axle bearings 1 60 60 Steering mechanisms 4 60 240 Clutch shaft 1 60 60 Starting crank bearing 1 60 60 Bolster bearing 1 60 60 23" 1380" Weekly or 60 Hours Air cleaner body, remove and clean 60 10 600 Fan belt, check tension 1 10 10 Generator belt, check tension 1 10 10 Radiator fins, clean 15 10 150 Storage battery, check level and fill 20 10 200 Grease fittings: Water pump bearing 1 10 10 Clutch release bearing 2 10 20 Clutch pilot bearing 5 10 50 Tires, a check pressure and inflate 10 10 100 TUT UsoT 120 Hours Crankcase oil, change 20 5 100 Oil filter element, change 15 5 75 Generator, lubricate _5 5 25 40 200 250 Hours Crankcase breather, remove and clean 30 3 90 Spark plug, remove and clean 30 3 90 Fuel strainer and sediment bowl, clean 5 3 15 "61 195" 300 Hours Starting motor, lubricate 5 2 10 Distributor cap, clean" 10 2 20 "IT 30 400 Hours Fuel line screen, clean 10 2 20 Engine valves, adjust 120 2 240 Clutch pedal, adjust 10 2 20 Brakes, adjust 20 40 Cooling system, flush and clean 30 2 60 190 380 * Not on maintenance guide sheet, but in the text of the manual. (Table concluded on next page) 1958] MAINTENANCE OF SIXTY FARM TRACTORS Table 7. concluded 31 ] Services Minute; equirec per service > Number I of services per year Total minutes re- quired 500 Hours Distributor breaker points, inspect .... . . 15 2 30 Distributor, lubricate 15 2 30 30~ 60 6 Months Front wheels, repack 90 2 180 90 180 1000 Hours Steering worm gear, change oil . . . . 50 1 50 Transmission and differential, change oil 50 1 50 Too Too Total time required to maintain tractor one year ... minutes 3675 hours 61.2 less time on maintenance chores than recommended by the manuals, it would seem desirable to reduce the number of chores and make the essential ones as easy to perform as possible. For example, the air cleaner, battery, steering mechanism, and valves currently require a great deal of maintenance time (Table 7) ; making these items easier to service would substantially decrease total maintenance time. Most companies are making an effort to reduce maintenance time. For example, on one current model tractor the battery can be moved to an accessible location and the liquid level checked without the use of wrenches. On the other hand, the generator of another current model cannot be lubricated without removing the hood, a process that neces- sitates the removal and replacement of eight screws with a special tool. Needless to say, this practice discourages proper generator lubrication. Comparatively few of the maintenance chores were standardized among various tractor makes and models. Table 7 shows intervals of 10, 60, 120, 250, 300, 400, 500, and 1,000 hours, and the operators in this study did not follow manual recommendations closely enough to justify so many maintenance intervals. Most operators did not recog- nize the difference between 250 and 300 or between 300 and 400 hours. The number of intervals should be kept to a minimum and could well be multiples of the crankcase oil change time. If the intervals were multiples, the operator could easily comply with recommendations. The following suggested schedule could serve as a guide for stand- ardizing recommendations on an industry-wide basis. It is set up in 32 BULLETIN NO. 624 [February, multiples of 100 hours. For example, at 200 hours, the operator would also perform the 100-, 50-, and 10-hour chores. The crankcase breather and other items for which current recom- mendations vary widely are not listed in this schedule. Transmission, steering gear, and power lift oil change have also been omitted. Studies should be made to determine if these services are really necessary. If they are necessary and farmers will not perform them, then tractors should be designed either to simplify these services or eliminate them. For example, a lifetime filter could be built into the transmission. 10 Hours (Daily) Engine oil level check Radiator level check Air cleaner cup inspection (change oil and clean cup when dirt reaches 14" to i/" depth or oil becomes contaminated) Grease fittings, steering, rear axle, etc. 50 Hours (One Week) Battery liquid level check Hydraulic system level inspection 100 Hours (Two Weeks) Engine oil change Engine oil filter change (or at 200 or 300 hours) Tire pressure check Generator lubrication 200 Hours (One Month) Spark plug inspection Ignition points inspection Distributor and cam lubrication Belt tension checks Starter lubrication (if required) Fuel strainer and sediment bowl 400 Hours (Two Months) Valve clearance check Transmission oil level check Steering gear oil level check Air cleaner, complete cleaning Yearly Clutch adjustment inspection Brake adjustment inspection Front wheels, clean and repack bearings Governor speed check Engine timing check Radiator flush Dealer tuneup 7958J MAINTENANCE OF SIXTY FARM TRACTORS 33 RECOMMENDATIONS This study of tractor manuals as related to the practices and opin- ions of the operators and the condition of their tractors is the basis for the following recommendations. STANDARDIZING MAINTENANCE INTERVALS All manufacturers should attempt to standardize the maintenance intervals for as many parts as possible. These maintenance intervals could be set up for daily service and in multiples of the time for crank- case oil change. Sixty hours or multiples of 60 hours cause confusion, but an interval of 100 hours is easy to determine on hour meters and odometers. To facilitate standardization of recommendations and to further investigate improved maintenance, it is suggested that the Farm Equip- ment Institute, American Society of Agricultural Engineers, and Society of Automotive Engineers establish a joint committee that would include representatives from all tractor manufacturers. This committee would have objectives similar to those of the CIMTC Ease of Maintenance subcommittee of the Society of Automotive Engineers. MAKING RECOMMENDATIONS REALISTIC Manufacturers should critically review each recommendation to make sure that it is both practicable and realistic. They should also encourage their designers to eliminate as many maintenance chores as possible and to make necessary chores easy to perform. IMPROVING INSTRUCTION MANUALS Those responsible for compiling and editing service manuals should be certain that their manuals contain only one specific recommendation for each item. Conflicting statements confuse the reader and leave him with no definite impression of what to do. Terms such as "periodic," "occasionally," "when needed," "fre- quently," "at intervals," and "maintain clearance" mean little to the farmer and should not be included in tractor manuals. Inspection intervals should be spelled out in actual hours of time, and limits of adjustment or condition should be given in such terms that the operator knows whether adjustment or service is needed at the time of inspection. 34 BULLETIN NO. 624 [February, Instruction manuals should also contain one page that lists all the lubrication and maintenance intervals and all the items to be serviced at each interval. FASTENING METAL REMINDERS ON TRACTORS Since many farmers seldom refer to their instruction manuals but need a constant reminder of necessary maintenance chores, it is also suggested that an abbreviated maintenance schedule be placed on a metal plate and fastened to the tractor dash in full view of the oper- ator. This plate and the hour meter might be color coded to make them easy to read. (See Fig. 9 for an example of an abbreviated schedule.) A metal plate might also be used to designate spark plug gap, igni- tion point clearance, valve clearances, and special recommendations when one manufacturer's recommendation differs widely from those of other manufacturers. Tire manufacturers could also return to the prac- tice of molding minimum inflation pressure into the sidewalls of their tires. IMPROVING COMMUNICATION BETWEEN FARMERS AND MANUFACTURERS Tractor maintenance is not just the concern of an individual com- pany for its own tractor it is a problem that affects the entire industry. To teach the farmer proper maintenance practices, each com- pany needs the cooperation of other tractor companies, the oil compa- nies, and college extension workers. Farm tractor manufacturers, particularly those who design parts and determine maintenance chores, can do much to improve tractor care. Petroleum salesmen contact farmers frequently and could help with maintenance problems if their companies would provide them with training and literature on tractor care. Service engineers and extension workers should keep close liaison with tractor manufacturers in order to maintain a steady flow of infor- mation in both directions. Tractor troubles resulting from maintenance deficiencies should be reported to the company engineers. The operator should be given a reason for following the recommen- dation, and manuals, maintenance bulletins and circulars, and state- ments by extension workers, service engineers, and petroleum salesmen should tell why a particular chore needs to be done. Since many of the neglected maintenance chores have a yearly interval of service, the dealer's yearly tuneup should also be encouraged. 7958J MAINTENANCE OF SIXTY FARM TRACTORS 35 ? o "^ Q ^ ^ ^ ^ C r> 2 Q ^ 4> 1 . o o> c s /> < ^ "W" o ^ 2 Q C Ul O 41 ^ < CM ^_ 6 -^ 3 ui *~ y ui < . 2 i 41 .t a. "" Q Ul o < O > e iz $ ui Ul k_ (/> E ^ a (M iH Q. .5! ui ^_ S *" 5 1 41 5 to o c O * o 2 oc UJ Q ? c | 8 5 al| .4 -1 (/> *> .2 a. a o O 1 C >, s fsi! UJ a. 5 UJ > or 32-SAE 20, B ) Level With Em In Kerosene - ings - Chassis Antifreeze For 4) S < ui . < s? e IO C * o !>- C .- a, i g'tc w Ul O M | U) S eo 2 O (M 0" M J3 e 10 5 - "c W o E < 1 o> E s r o 2 5 | > ' " So H a ro o ^ 4> O <0 _l Ol _ 4* O M & 0> c c o O 5 . o UJ 1 = 1 i o. ii ^ B 6 2 a. a, a. j<: O >. O . O 1 4) ^ 5 x .2 1- S < U. $ 00 Q z < o (/) u. O O O _ H CC U. * Ul o uT V) M 41 t o. | | ~ c O 03 'c o 0. CO E c UJ Q. O je ' ^5 C7 1 C o o c | ^ 4> 41 5 = I -5 <- ^ t C O) W 41 41 _ 8 | J. J 41 _ _l JC ^ -o " > 41 o o 41 > i E 41 u 4) .E ~ 4 a O $5 " 1 _| ^j U. 'C t: o o "* . c !; -- o o ^ c c S 2 g -o a: iZ 15 s * - 4> o " |5 Sjg * j 5 (A 6 | S o> o o o c i w O O J E S o o -^ o* a 2 e c "* I S 41 _ 41 w* 3 41 ^ ft- 22 ^ iz 4> C ^ E C ._ |s | ? i !_ O 01 1 I 2 2 ui < o o cr ffi X Ul O t- O O (/) 03 U. < f- W > O O U. H M >> o 2 o 5! o S i 2 | o '5 S 8 g = f\l o g e x X ~ x N I z V S V / /rS o W1 o bfl rt ir* i-. X +J o 4-> T3 4J 03 <+4 U .2 U y 2 36 BULLETIN NO. 624 [February, SUMMARY In the summer and fall of 1955, 60 tractors (ten models represent- ing eight different makes) on farms in central Illinois were inspected for evidence of good or poor maintenance practices. During the inspec- tion, the operator was questioned on his knowledge of the manual recommendation for each maintenance item, his opinion as to how often the item should be serviced, and his actual practice in servicing it. Analysis of the inspections and operator interviews revealed the following results: 1. Maintenance chores were being neglected. 2. Operators of all ages gave their tractors about the same de- gree of care, and there was little difference in the maintenance levels of the ten models. 3. The most frequent maintenance deficiencies were dirty crank- case breathers and air cleaners, batteries with liquid level below the plates, low tire pressure, improper valve adjustment, pitted ignition points, poorly adjusted brakes, excessive engine speed, and crankcase oil that needed changing. 4. To improve maintenance, each of these items must be con- sidered separately. Most operators were following manual recommenda- tions for battery care and crankcase oil change. Only a few operators were following manual recommendations for air cleaner and crankcase breather service, tire pressure check, and valve clearance adjustment. 5. The life of spark plugs, valves, batteries, pistons, rings, sleeves, and certain other parts varied more among tractor models than between tractors of the same model. 6. The fact that an operator knew a certain recommendation did not necessarily mean that he was following it. Many recommendations were not followed because the operator felt that they were unnecessary, time-consuming, messy, or expensive. 7. Operator education was best on those items for which the manual recommendation was both standardized and specific. Operator education was poorest on those items for which there was no manual recommendation or no standardization of the recommendation among tractor manuals. 8. Following present manual recommendations to the letter re- quires about 60 hours a year or 10 percent of the tractor's operating time. The farmers interviewed in this study were spending much less than 60 hours a year on tractor maintenance. J958J MAINTENANCE OF SIXTY FARM TRACTORS 37 APPENDIX SUMMARY OF TRACTOR INSPECTIONS Not all items were inspected on all 60 tractors because some tractors did not contain certain parts. For example, a Diesel tractor does not have spark plugs. Item inspected Number of tractors Air cleaner, vacuum test a O.K. Oto3"H 2 ........... 41 3 to 5" ...................... 4 Over 5" ..................... 4 Air cleaner, precleaner or screen Clean ....... . ............... 43 Needed cleaning ............. 15 Contained oil ................ 1 Broken ..................... 1 Air cleaner, dirt in bowl O.K ........................ 14 Y* to Yi of dirt ............. 29 Over Y? of dirt .............. 17 Air cleaner, oil level O.K 39 M"to ^ ff low ............... 19 Over ]/%' low ................ 2 Air cleaner, oil viscosity SAE 10 ..................... 3 SAE 20 ..................... 38 SAE 30 ..................... 18 Air cleaner body Clean ....................... 29 Dirty ....................... 27 Nearly plugged .............. 2 Hole in inlet ................. 2 Air cleaner hose O.K ........................ 44 Loose ...................... 1 Defective clamp ............. 10 Battery liquid level O.K ........................ 33 High ....................... Low ........................ 27 Below plates ................ 16 Battery hydrometer reading 1.28 to 1.25 ................. 30 1.25 to 1.22 ................. 7 1.22 to 1.19 ................. 5 1.19 to 1.16 ................. 3 Below 1.16. . 1 Item inspected Number of tractors Test made at full-throttle, no-load speed. Battery condition O.K ........................ 26 Corroded terminals ........... 32 Loose terminal ............... 1 Loose in holder .............. 2 Corroded box ................ 1 Defective cable .............. 1 Brakes, adjustment O.K ........................ 35 Needed adjustment .......... 25 Uneven ..................... 19 Pedal stuck ................. 1 Carburetor, load adjustment O.K ........................ 40 Too rich .................... 9 No response to adjmt ......... 1 Carburetor, idle adjustment O.K ........................ 32 Too fast .................... 6 Too slow .................... 1 Too rich .................... 11 Too lean .................... 1 No response to adjmt ......... 8 Carburetor float level O.K. + Ke" .................. 27 Y% high .................... 11 8 1 M'low ..................... 3 Clutch free play O.K ........................ 47 Too much ................... 8 Not enough ................. 3 Pedal stuck ................. 2 Pedal bearing worn ........... 2 Crankcase breather O.K ........................ 10 Dirty ....................... 32 Apparently plugged .......... 12 Differential oil level O.K.^" ................... 43 4 3 10 to high Over K"low 38 BULLETIN NO. 624 [February, Item inspected Number of tractors Item inspected Number of tractors Distributor cap O.K 40 Corroded terminals 7 Dirty 3 Corroded rotor 1 Dust cap broken 1 Distributor points O.K 19 Pitted 27 Worn 4 Misaligned 1 Distributor point gap O.K. .002 27 .002 to .005 too wide 1 Over .005 too wide 3 .002 to .005 too close 11 Over .005 too close 6 Distributor cam O.K 29 Dry 3 Excessive lubrication 13 Dirty 4 Engine oil pressure Normal 55 High 2 Gage not working 3 Engine oil level O.K 32 1 quart low 22 More than 1 quart low 5 1 quart high 1 Engine oil viscosity SAE 10 3 SAE20 42 SAE 30 14 SAE 40 1 Engine oil acidity Alkaline 1 5 2 11 Neutral 3 30 4 11 Acid 5 3 Engine oil spot test Clean 39 Carrying light dirt load 13 Carrying heavy dirt load 8 Dispersing O.K 56 Dispersing inadequately 3 Silica present 11 Needed change 24 Engine oil filter O.K 29 Needed change 11 No filter . . 1 Engine timing O.K. 3 degrees 41 4 to 8 degrees slow 6 8 to 12 degrees slow 2 4 to 8 degrees fast 4 8 to 12 degrees fast 1 Fan belt condition O.K 31 Defective 18 Too loose 19 Too tight 5 Front wheel bearing adjustment O.K 38 Too loose 19 Left 7 Right 6 Front wheel bearing lubrication O.K.. . 48 Repacking needed 4 Front wheel bearing seal O.K 51 Needed replacement 4 Fuel filter O.K 6 Dirty 28 Damaged 2 Fuel sediment bowl Clean 7 Contained water 8 Dirty 48 Leaking 2 Gaskets (leaking) Valve cover 7 Crankcase 7 Cylinder head 2 Differential 3 Transmission 4 Hydraulic system 4 Rear axle 1 Belt pulley seal 1 Front bolster 1 Carburetor 1 Generator belt condition O.K 34 Defective 19 Too loose 21 Too tight 2 Generator and regulator O.K. . 57 Excessive charge 1 Not charging 2 Governor no-load speed O.K. 30 engine r.p.m 18 30 to 60 too fast 8 7958J MAINTENANCE OF SIXTY FARM TRACTORS 39 Item inspected Number of tractors Item inspected Number of tractors Governor no-load speed cont. Over 60 too fast 24 30 to 60 too slow 1 Over 60 too slow 5 Hydraulic system condition O.K.. 53 Leaking 4 Hydraulic system oil level O.K Low High .. 25 25 3 PTO clutch adjustment O.K 57 No PTO clutch 3 Radiator cap and overflow O.K. . 57 Defective 3 Radiator leaking 3 Overflow defective 4 Radiator screen Clean 36 Dirty 5 Damaged 4 No screen 15 Radiator fins Clean 24 Dirty 36 Bent 2 Radiator hose O.K.. 44 Leaking 8 Loose clamp 2 Defective hose 6 Top hose leaking 5 Radiator water Level O.K 46 Level low 14 Clean 35 Dirty, rusty or oily 6 Rear axle spline O.K 11 Rusty 35 Spark O.K 48 Weak 7 Spark plug wires O.K. 50 Faulty insulation 5 Corroded terminals 4 Damaged ends 1 Spark plug range Correct 52 Too hot 2 Too cold . . 1 Spark plug condition O.K ........................ 49 Cracked porcelain ............ 3 Too loose ................... 2 Gasket missing .............. 2 Spark plug deposits Clean ..... . ................. 21 Lead deposits ................ 16 Carbon deposits ............. 18 Fouled ...................... 4 Spark plug gaps O.K. -.002 to +.005 ......... 20 Under -.002 ................ Over +.005 ................. 35 Steering gear adjustment O.K ........................ 30 Too loose ................... 30 Tire condition, front Practically no wear ........... 18" Moderate wear .............. 66 Excessive wear .............. 35 Damaged ................... 18 Cracked .................... 4 Tire pressure, front O.K. 2 p.s.i ................. 45 a 3 and 4 p.s.i. low ............. 4 Over 4 p.s.i. low ............. 29 3 and 4 p.s.i. high ............ 8 Over 4 p.s.i. high ............ 34 Tire condition, rear Practically no wear ........... 22 a Moderate wear .............. 81 Excessive wear .............. 13 Damaged ................... 15 Tire pressure, rear O.K. 12 to 16 p.s.i ............ 60 a 1 and 2 p.s.i. low ............. 27 2 and 3 p.s.i. low ............. 11 Over 4 p.s.i. low ............. 13 1 and 2 p.s.i. high ............ 7 2 and 3 p.s.i. high ............ 2 Transmission oil level O.K. + M" M" to y? high Over W high 1^" to H" low 39 6 1 3 Over y 2 " low ................ 11 Valve clearances, intake O.K. + .002 .................. 101 b .002 to .005 too wide ......... 40 Over .005 too wide ........... 40 .002 to .005 too close ......... 17 Over .005 too close. . ... 12 a Number of tires from total of 120. b Number of valves from total of 210. 40 BULLETIN NO. 624 [February, Item inspected Number of Item tractors inspected Valve clearances, exhaust O.K. + .002 75 b .002 to .005 too wide 48 Over .005 too wide 57 .002 to .005 too close 16 Over 005 too close 14 Water pump belt condition O.K 28 Too loose 17 Too tight 5 Defective. . . 14 Number of tractors General tractor condition Clean 15 Dirty 45 Oily 5 Estimate of over-all maintenance Excellent 2 Good 25 Fair 26 Poor. . 7 b Number of valves from total of 210. SUMMARY OF OPERATORS' ANSWERS TO PERSONAL INTERVIEW The operators' answers were summarized as follows: A = operators' actual practices B = operators' answers to quiz on manual recommendations C = operators' opinions as to frequency of service necessary Since the tractors inspected were of ten different models, and rec- ommendations differed among models, the information in this summary should be used with discretion. Number of Item answers A B C Air cleaner cup check 2 times daily 2 1 Daily 9 39 15 2 times weekly 20 2 16 Weekly 12 1 10 2 weeks 6 1 4 Monthly 7 1 6 2 to 6 months 5 3 At oil change 2 1 1 Oftener when operating conditions dusty. . . . 5 1 3 No answer 16 1 Air cleaner oil change When dirt W deep .... 6 2 5 When dirt W deep .... 6 6 7 Daily 8 22 11 Twice a week 9 8 Weekly 5 3 5 60 hours 8 2 5 100 hours 13 1 9 At oil change 4 1 3 No answer 23 7 Item Air cleaner, type of oil New Number of answers ABC 53 38 49 555 52 35 49 232 646 ng 2 .. 1 Used Same weight as crankcase Heavier weight . . Lighter weight Air cleaner, complete cleani 60 hours . ... 100 hours 4 times yearly 1 11 21 3 1 1 9 12 4 25 7 19 2 times yearly 7 7 6 3 1 35 4 9 - 2 2 41 3 16 '6 Yearly 2 years . 4-7 years . When needed Never No answer Battery liquid level check Twice a week 1 23 8 21 Weekly 2 weeks Monthlv. . J958J MAINTENANCE OF SIXTY FARM TRACTORS 41 Number of Item answers A B C Battery liquid level check cont. 2-3 times per year 5 3 Yearly 1 1 1 At oil change 1 1 No answer 34 Battery water used Rain water 14 6 13 Well water 33 2 28 Distilled water 9 24 10 Soft water 3 2 From dehumidifier 2 2 No answer 28 5 Belt tension checks 2-3 days 4 4 1-2 weeks 10 3 9 Monthly 14 2 12 3 months 3 2 6 months 7 5 Yearly 5 6 When engine gets hot . . . 5 1 3 When needed 12 2 7 No answer 52 12 Brake adjustment 400 hours 2 1 1 Yearly 12 3 10 2-3 years 2 1 2 4-6 years 4 2 When needed 32 7 24 Never 7 1 No answer 1 48 20 Carburetor adjustment 6 months 5 5 1-3 years 1 1 According to job 23 1 15 According to weather. . . 1 When needed 11 2 8 Never 15 1 3 No answer 4 55 29 Clutch bearing lubrication Twice daily 1 Daily 9 7 7 Twice a week 9 2 9 Weekly 8 5 10 2-4 weeks 4 1 3 6 months 4 1 3 None required 15 7 7 No answer 11 36 21 Clutch adjustment 400 hours 3 2 6 Yearly 6 3 7 2-4 years 8 5 When needed 25 3 24 Never 16 3 No answer 2 52 15 Item Number of answers ABC Crankcase breather service Daily ................. 5 Twice a week .......... 1 Weekly ............... 9 Monthly ................ 6 months ............. 4 Yearly ................ 10 2-5 years .............. 3 Never ................ 17 Not required .......... 11 No answer .............. Crankcase flush Yes .................. 9 No... ................ 48 Occasionally ........... 2 Once or twice yearly .... 2 Distributor lubrication Every 3 days .......... 1 60 hours .............. 4 120 hours ............. 1 250 hours ............. 5 500 hours ............. 8 When points are changed 1 None required ......... 22 With magnetos ........ 8 No answer ............ 10 Distributor point adjustment 6 months ............. 9 Yearly ................ 13 2 years ............... 4 When new ones installed 2 When needed .......... 11 Never ................ 7 No answer ............ 9 Engine oil level check Twice daily ........... 17 Daily ................. 35 Twice weekly .......... 3 Weekly ............... 1 Monthly .............. 1 At start of job ......... 3 No answer .............. Engine oil change 40 hours .............. 5 50 hours .............. 2 60 hours .............. 23 70 hours .............. 3 80-90 hours ........... 2 100 hours ............. 9 120 hours ............. 7 150 hours ............. 2 200-300 hours ......... 3 When oil is dirty ....... 2 No answer. . 2 29 3 6 1 9 3 9 . . 1 .. 2 4 15 41 4 14 10 19 46 . . 1 1 3 1 4 12 1 .. 1 17 42 24 4 9 5 13 . . 3 . . 2 .. 6 2 1 44 21 7 18 35 36 . . 2 .. .. . . 1 1 2 17 6 6 1 2 17 22 . . 3 42 BULLETIN NO. 624 [February, Number of Number of Item answers Item answers A B C A B C Engine oil filter change Fuel sediment bowl service Every oil change 25 14 24 Daily 1 Every second change . . . 19 12 18 60 hours 3 2 5 Every third change. . . . . 3 1 3 120 hours 3 3 5 120-150 hours . 2 4 2 250 hours 3 1 7 2-3 times yearly 8 3 7 500 or more 14 5 11 Yearly 4 3 When needed 33 1 21 When oil is dirty ? 1 1 Never 4 2 No answer 25 2 No answer 47 9 Engine oil consumption Fuel type used None in 60 hours 22 Regular gasoline 50 25 39 .5 quart . 4 Premium 1 1 1 quart >o LPgas 5 5 5 2 quart . 5 Diesel #1 2 2 2 3 quart . 1 Diesel #2 3 2 2 4 quart . 4 No answer 25 11 Over 4 quarts 2 Engine oil viscosity (summer) SAE 10W-30 2 SAE 20-20W 20 SAE 30 36 10 29 1 18 35 Fuel storage tank Overhead tank Underground 1200 gallon 1000 40 12 1 s 2 2 1 15 23 1 SAE 40 7 2 2 500 16 1 8 No answer 19 4 300 28 9 Engine oil viscosity (winter) 150 2 SAE 10W-30 . 3 2 SAE 20W-40 SAE 10-10W SAE 20-20W SAE 30 17 29 11 1 21 17 2 17 28 10 Fuel storage cap Weighted Open vent Pressure vacuum 17 25 5 2 1 1 19 17 5 No answer 19 3 Front wheel lubrication Engine oil, API class Daily 1 1 1 ML regular MM premium MS\ 01 . 1 5 20 3 T, 1 3 17 Weekly Monthly 6 months 2 7 1 1 13 '2 9 DG/ S 7? 1 16 Yearly 28 19 31 DS S 2 3 9 3 2 years 11 9 No answer 9 51 7.0 3 years or longer 4 2 Never / 1 Engine timing No answer 25 5 6 months 2 1 2 Yearly 8 4 9 Front wheel, type of lube 2 years 3 2 Transmission oil 6 4 5 At overhaul , 3 3 Gun grease 50 27 47 When needed 14 3 11 Fiber grease 2 2 2 Never ?1 6 11 No answer 2 27 6 No answer 4 41 17 Generator lubrication Engine tuneup Twice daily 1 1 1 Every 6 months 6 1 6 Daily 4 3 4 Yearly S? 9 26 Every other day 1 1 1 2 years 7 3 60 hours 19 14 19 At major overhaul .... 4 1 120 hours 15 8 17 When needed 1? 7 250 hours 11 1 10 By dealer's mechanic. . . 24 14 23 3 months 2 1 2 By other mechanic. . . . S 2 Yearly 2 2 By owner 3 1 1 No answer 5 31 4 J958J MAINTENANCE OF SIXTY FARM TRACTORS 43 Item Number of answers ABC Item Number of answers ABC Governor adjustment 6 months ............. 1 Yearly ................ 4 2 years ................. When gives trouble ..... 2 When needed .......... 14 According to load ...... 2 Never ................ 35 No answer ............ 2 Grease fittings, rear axle Twice daily ........... 1 Daily ................. 21 Twice weekly .......... 10 Weekly ............... 9 Monthly .............. 1 6 months ............. 3 Infrequently ........... 10 No answer ............ 5 Grease fittings, steering Twice daily ........... 4 Daily ................. 28 Twice a week .......... 10 Weekly ............... 12 Monthly .............. 2 6 months ............. 3 Infrequently ........... 1 No answer .............. Hydraulic system, level check Daily ................. 12 Twice weekly .......... 4 60-120 hours .......... 11 1-4 times a year ....... 10 Before using ........... 8 No answer ............ 15 Hydraulic system oil change 1-4 months ............ 1 3-6 months ............ 1 1-2 years .............. 17 Never ................ 30 No answer ............ 11 Hydraulic system oil type SAE 10 ............... 10 SAE 20 ............... 17 SAE 30 ............... 9 Special hydraulic ....... 10 No answer.. .......... 14 Hydraulic system flush Yes .................. 4 No ................... 40 No answer ............ 16 Radiator level check Daily ................. 7 Twice weekly .......... 32 Weekly ............... 6 Monthly .............. 10 When it gets hot ....... 6 No answer . . . . 1 1 7 3 2 5 11 . . 2 .. 17 51 20 2 1 17 19 1 11 6 9 . . 1 3 8 8 1 7 26 4 3 26 28 1 12 4 10 1 2 . . 2 . . 1 24 2 12 12 1 4 4 11 . . 6 . . 8 43 19 2 3 6 4 10 14 . . 11 42 28 5 9 13 15 58 6 6 31 22 13 30 40 21 46 30 32 1 7 .. 12 . . 3 25 Radiator flush Twice a year .......... 15 Yearly ................ 26 2 years or more ........ 5 Never ................ 13 No answer ............ 1 Spark plug inspection 100 hours ............. 1 200 hours ............. 12 500 hours ............. 3 2-3 times a year ....... 8 Yearly ................ 6 When engine misses. ... 18 Never ................ 10 No answer .............. Spark plugs, replaced 250 hours ............. 6 500 hours ............. 13 Yearly ................ 10 2-3 years .............. 11 When needed .......... 14 Not replaced .......... 4 No answer .............. Starter lubrication Daily ................. 2 2-3 days .............. 2 60 hours .............. 5 120 hours ............. 9 250 hours ............. 5 2-3 times yearly ........ 3 Yearly ................ 2 None required ......... 30 No answer ............ 2 Steering gear oil level check Monthly .............. 1 6 months ............. 6 Yearly ................ 27 At overhaul ........... 7 Never ................ 16 No answer ............ 3 Steering gear oil change 6 months Yearly ................ 1 Never ................ 43 No answer ............ 16 Tire pressure check Twice weekly ............ Weekly ............... 2 2 weeks ............... 2 1-2 months ............ 7 2-3 times yearly ....... 6 Yearly ................ 3 When looks low ........ 40 According to job ....... 1 No answer. . 8 14 14 30 . . 1 . . 3 38 12 3 4 4 17 1 3 4 11 1 3 1 4 37 1 5 16 2 7 7 .. 8 3 3 43 6 1 2 1 2 3 6 5 8 .. 5 .. 2 2 18 21 32 12 1 1 7 7 12 28 4 3 40 17 , 1 3 1 6 36 51 22 1 6 2 6 4 2 .. 23 1 48 15 44 BULLETIN NO. 624 Number of Item answers ABC Transmission oil level check Daily 1 1 1 Weekly 1 2 1 Monthly 887 2-3 times yearly 22 9 26 Yearly 24 8 22 2 years 3 . . 1 No answer 1 32 2 Transmission oil change 6 months 2 Yearly 5 2 years 3 3-4 years 4 5-6 years 3 At overhaul 3 Never 39 No answer 1 Transmission oil type (summer) SAE 80 4 2 5 SAE90 21 14 20 SAE 140 16 13 12 Special hydraulic 2 No answer 17 31 23 Transmission oil type (winter) SAE 80 4 3 6 SAE 90.. . 23 16 22 11 1 18 14 4 4 4 1 2 1 '3 18 23 16 Number of Item answers ABC Transmission oil type (winter) cont. SAE 140 13 5 8 Add fuel oil 2 No answer 20 34 24 Transmission flush Yes 11 18 20 No 30 10 25 No answer 19 32 15 Valve clearance check 200 hours 3 3 7 500 hours 10 7 16 Yearly 948 2 years 4 . . 2 At overhaul 6 . . 2 When valves noisy 6 . . 3 Never 18 2 2 No answer 4 44 20 Water pump lubrication Daily 988 Every 2 days 3 . . 3 Weekly 9 4 10 Monthly 1 1 1 Every 4 months 3 . . 3 Not required 21 14 14 No answer.. .14 33 21 LITERATURE CITED 1. GATES, V. A., BERGSTROM, R. F., and WENDT, L. A. Further discussion on "oil spot" evaluation of used engine lubricants. Paper presented at Soc. Automotive Engin. National West Coast meeting, 1955 (preprint No. 572). 2. ILLINOIS AGRICULTURAL EXPERIMENT STATION. Progress in solving farm problems in Illinois. 111. Agr. Exp. Sta. Nine- Year Rpt. (1938- 1947): 154- 158. 1948. 3. NAVARIN, R. C, and Usow, K. Design and ease of maintenance. Paper presented at Soc. Automotive Engin. Tractor meeting, 1955 (preprint No. 580). 4. SHAWL, R. I. Tractor repair and maintenance. 111. Agr. Col. Ext. Cir. 589 :4r S.* SMITH, C. W., and LARSEN, L. F. Factors affecting the efficiency of farm tractors. Paper presented at Soc. Automotive Engin. Tractor >,. meeting," 1 952 (preprint No. 805). 6. WEBER, J. A. Valve life study of sixty farm tractors. Paper presented at S6d! Automotive Engin. Tractor meeting, 1955 (preprint No. 587). 6M-