1. Standard Transmission Servicing
Chapter 16
Standard Transmission
Servicing

2. Objectives (1 of 2)
Explain the importance of using the correct lubricant and maintaining the correct oil level in a transmission.
List the preventive maintenance inspections that should be made periodically on a standard transmission.
Explain how to replace a rear seal.
Describe the procedure for troubleshooting standard transmissions.
Objectives
After reading this chapter, you should be able to
• Explain the importance of using the correct lubricant and maintaining the correct oil level in a transmission.
• List the preventive maintenance inspections that should be made periodically on a standard transmission.
• Explain how to replace a rear seal.
• Describe the procedure for troubleshooting standard transmissions.
• Identify the causes of some typical transmission performance problems, such as unusual noises, leaks, vibrations, jumping out of gear, and hard shifting.
• Outline the procedure for overhauling a transmission.
• Analyze the procedure for performing failure analysis on transmission components.
• Troubleshoot an air shift system.

3. Objectives (2 of 2)
Identify the causes of some typical transmission performance problems, such as unusual noises, leaks, vibrations, jumping out of gear, and hard shifting.
Outline the procedure for overhauling a transmission.
Analyze the procedure for performing failure analysis on transmission components.
Troubleshoot an air shift system.
Objectives
After reading this chapter, you should be able to
• Explain the importance of using the correct lubricant and maintaining the correct
oil level in a transmission.
• List the preventive maintenance inspections that should be made periodically on a standard transmission.
• Explain how to replace a rear seal.
• Describe the procedure for troubleshooting standard transmissions.
• Identify the causes of some typical transmission performance problems, such as unusual noises, leaks, vibrations,
jumping out of gear, and hard shifting.
• Outline the procedure for overhauling a transmission.
• Analyze the procedure for performing failure analysis on transmission components.
• Troubleshoot an air shift system.

4. Recommended Lubricants
Recommended lube
Use only the recommended lube.
Synthetic lube
Most transmission manufacturers today prefer synthetic lubricants.
E-500
Eaton recommends E-500 lubricant. It is designed to run 500,000 linehaul miles with no initial drain interval required.
E-250
Lubricant is rated for 250,000 linehaul miles before a change is required.
Synthetics exceed requirements
They can be expected to perform effectively through various geographic and seasonal temperature conditions.
RECOMMENDED LUBRICANTS
Only the lubricants recommended by the transmission manufacturer should be used in the transmission. Most transmission manufacturers today prefer synthetic lubricants formulated for use in transmissions; they also suggest a specific grade and type of transmission oil. In the past, heavy-duty engine oils and straight mineral oils tended to be more commonly used in truck transmissions, but demand for extended transmission lube service intervals has driven the industry toward using synthetics almost exclusively. Today, Eaton recommends E-500 lubricant for its transmissions. E-500 lube is designed to run 500,000 linehaul miles with no initial drain interval required. E-250 lubricant is rated for 250,000 linehaul miles before a change is required. Most synthetic transmission lubricants exceed the stated viscosity grade ratings, so they can be expected to perform effectively through various geographic and seasonal temperature conditions.

5. Mineral-based Lubes Initial oil change Oil change intervals
Will flush out of the transmission any cutting debris created by virgin gears meshing
Linehaul
Any time after 3,000 miles, but before 5,000 miles
Off-highway
After 24 and before 100 hours of service
Oil change intervals
Linehaul: Oil change intervals vary between 50,000 and 100,000 miles for linehaul applications.
Off-highway: Off-highway operation usually requires oil change intervals ranging from 1,000 hours to a maximum of 2,000 hours of service.
Mineral-Based Lubes
Most manufacturers recommend an early initial oil change after the transmission is placed in service when using mineral-base gear lubes. It is usually recommended that this first oil change be made any time after 3,000 miles but before 5,000 miles of linehaul road service. In off-highway use, the first transmission oil change should be made after 24 and before 100 hours of service. Although transmission oil is never required to be changed as frequently as engine oil, this first oil change is important because it will flush out of the transmission any cutting debris created by virgin gears meshing. A number of factors influence the appropriate scheduling of mineral-based transmission oil change periods. A key factor is the application: Linehaul operation tends to be kind to transmission oil, while operating on a construction site can reduce performance life. Manufacturer suggestions for mineral based transmission oil change intervals vary between 50,000 and 100,000 miles for linehaul applications. Off-highway operation usually requires oil change intervals ranging from 1,000 hours to a maximum of 2,000 hours of service. In each housing, the type of oil used can influence the oil change interval. Practice shows that using synthetic lubricants can extend the performance life of the oil.

6. Synthetic-based Lubes
E-500: E-500 is designed for 500,000 linehaul miles.
Initial drain: The initial drain interval, once considered so important to maximize transmission service life, can be eliminated.
E-250: E-250 lubricant is rated for 250,000 linehaul miles.
Synthetic-Based Lubes
Because transmission manufacturers almost exclusively recommend the use of synthetic gear lubes today, it follows that older, mineral-based lubes are not a realistic option. Eaton recommends E-500 lube for its transmissions. E-500 lubricant is designed to run 500,000 linehaul miles. Furthermore, when using E-500 lubricant, no initial drain interval is required for the transmissions. Modern production machining accuracy has all but eliminated the tendency of a gearset to produce break-in cuttings when new. As a result, the initial drain interval, once considered so important to maximize transmission service life, can be eliminated. E-250 lubricant is rated for 250,000 linehaul miles before a change is required. Synthetic lubricants formulated for transmissions exceed the stated viscosity grade ratings, so they can be expected to perform effectively through various geographic and seasonal temperature conditions. It is important that synthetic lubricants not be mixed with mineral-based lubes in transmissions. Although mixing of dissimilar lubricants may not produce an immediate failure, the service life of the lube can be greatly reduced. Mixing dissimilar lubricants can sometimes thicken the oil and produce foaming.

7. Caution
Do not add transmission lubricant without first checking what lubricant the transmission is using.
Mineral-based gear oils, mineral-based engine oils, and synthetic gear lubes are all approved for use in transmissions and none of them are particularly compatible. Mixing transmission oils causes accelerated lube breakdown, resulting in lubrication failures.
CAUTION!
Do not add transmission lubricant without first checking what lubricant the transmission is using. Mineral-based gear oils, mineral-based engine oils, and synthetic gear lubes are all approved for use in transmissions and none of them are particularly compatible. Mixing transmission oils causes accelerated lube breakdown, resulting in lubrication failures.

8. Checking Oil Level
Check at each A-type service, typically at intervals of 5,000 or 10,000 highway miles.
Avoid mixing brands, weights, and types of oil.
The transmission oil level should be exactly even with the filler plug opening as shown.
Overfilling can cause oil aeration.
Under-filling results in oil starvation.
Checking Oil Level
The transmission oil level should be routinely checked at each A-type service, typically at intervals of 5,000 or 10,000 highway miles. When adding oil to transmissions, care should be taken to avoid mixing brands, weights, and types of oil. When topping up or filling the transmission oil level, it should be exactly even with the filler plug opening, as shown in Figure 16–1. Overfilling can cause oil aeration and underfilling results in oil starvation to critical components.

9. Shop Talk
Transmission oil should be exactly level with the filler plug opening.
One finger joint equals approximately one gallon of transmission oil, so testing oil level by dipping your finger into the oil filler hole is not a good practice.
Shop Talk
Transmission oil should be exactly level with the filler plug opening. One finger joint equals approximately one gallon of transmission oil, so testing oil level by dipping your finger into the oil filler hole is not a good practice.

10. Caution Do not overfill the transmission.
Overfilling usually results in oil breakdown due to aeration caused by the churning action of the gears.
Premature breakdown of the oil will result in varnish and sludge deposits that plug up oil ports and build up on splines and bearings.
CAUTION!
Do not overfill the transmission. Overfilling usually results in oil breakdown due to aeration caused by the churning action of the gears. Premature breakdown of the oil will result in varnish and sludge deposits that plug up oil ports and build up on splines and bearings.

11. Shop Talk
When draining transmission oil, check for metal particles in the oil.
Metal particles may indicate excessive wear and may warn of an imminent failure.
It is not unusual for a newly broken in transmission to have minute metal particles held to a magnetic drain plug.
When draining transmission oil, check for metal particles in the oil. Metal particles may indicate excessive wear and may warn of an imminent failure. It is not unusual for a newly broken in transmission to have minute metal particles held to a magnetic drain plug.

12. Preventive Maintenance Inspections
A good preventive maintenance (PM) program can help avoid failures, minimize vehicle downtime, and reduce the cost of repairs. Often, transmission failure can be traced directly or indirectly to poor maintenance. Figure 16–2 identifies key areas of a transmission that should be routinely checked. We have outlined here some typical good maintenance practices, but you should remember that some operating conditions may either raise or lower maintenance standards. The numbers used reference callouts in Figure 16–2.
Preventive maintenance (PM) can help avoid failures, minimize vehicle downtime, and reduce the cost of repairs.
Often, transmission failures can be traced directly or indirectly to poor maintenance.

13. Daily Maintenance During the drivers daily pre-trip: Air tanks
Drain air tanks to remove water or oil.
Oil leaks
Visually check for oil leaks.
Shifting performance
Report any shifting performance problems such as hard shift or jumping out of gear.
DAILY MAINTENANCE
Many of the practices listed here are part of the driver pre-trip inspection.
Air tanks. Drain air tanks to remove water or oil. To be sure of removing all liquid contaminants from an air tank, the drain cock must be fully opened and all air discharged. Most of the liquid will drain from the tank after the air has been bled.
Oil leaks. Visually check for oil leaks around bearing covers, PTO covers, and other machined surfaces. Check for oil leakage on the ground before starting the truck each morning.
Shifting performance. Report any shifting performance problems such as hard shift or jumping out of gear.

14. B Inspection PM Air control system Bell/clutch housing flange
Check for leaks.
Bell/clutch housing flange
Check fastener torque.
Clutch shaft yoke bushings
Grease clutch shaft bushings lightly.
Pry upward on the shaft to check for wear.
COE remote shift linkage
Lube U-joints and check for wear.
Check any bushings in the linkage for wear.
Air filter
Check and clean or replace the air filter element.
Transmission output yoke
Uncouple the U-joint and check the flange nut for proper torque.
Tighten if necessary.
Output shaft assembly
Pry upward on the output shaft to check radial play in the mainshaft rear bearing.
Check the splines on the output shaft for wear from movement and chucking action of the U-joint yokes.
B INSPECTION PM
Air control system (1). Check for leaks, worn hoses and air lines, loose connections, and loose fasteners.
Bell/clutch housing mounting flange (2). Check fastener torque.
Clutch shaft yoke bushings (4). If the clutch shaft bushings are equipped with zerk fittings, grease them lightly. Pry upward on the shaft to check for wear. If excessive movement is found, remove the clutch release mechanism and check for worn bushings.
COE remote shift linkage. Check the linkage U-joints for wear and binding. Lubricate the U-joints. Check any bushings in the linkage for wear.
Air filter. Check and clean or replace the air filter element.
Transmission output yoke (10). Uncouple the U-joint and check the flange nut for proper torque. Tighten if necessary.
Output shaft assembly (11). Pry upward on the output shaft to check radial play in the mainshaft rear bearing. Check the splines on the output shaft (12) for wear from movement and chucking action of the U-joint yokes.

15. C Inspection PM Oil life Gearshift lever Oil shift tower assembly
If an oil change is required, drain and refill the transmission with the specified oil.
Transmission oil analysis can be used to establish more precise oil change intervals that are better suited to the actual operating condition of the truck.
Gearshift lever
Check for bending and free play in the tower housing.
Oil shift tower assembly
Remove the air lines at the slave valve and remove the shift tower from the transmission.
Check the tension spring and washer for wear and loss of tension.
Check the gearshift lever spade pin/shift finger for wear.
Also take a look at the yokes and blocks in the shift bar housing, checking for wear at all critical contact points.
C INSPECTION PM
Check lubricant change interval. This means checking the type of lubricant used in the transmission. Remember that many synthetic lubes are performance rated for oil change intervals up to 500,000 linehaul miles, so it is wasteful to change them more frequently. If an oil change is required, drain and refill the transmission with the specified oil. Transmission oil analysis can be used to establish more precise oil change intervals that are better suited to the actual operating condition of the truck.
Gearshift lever (8). Check for bending and free play in the tower housing. A lever that is excessively loose indicates wear. Shift tower assembly (9). Remove the air lines at the slave valve and remove the shift tower from the transmission. Check the tension spring and washer for wear and loss of tension. Check the gearshift lever spade pin/shift finger for wear. Also take a look at the yokes and blocks in the shift bar housing, checking for wear at all critical contact points.

16. Preventive Maintenance Recommendations
See Table 16-1 on page 469 of the textbook.

17. Caution
Using a 1-inch air gun to tighten yoke retaining nuts should be avoided, although it is all right to remove the nut using this tool.
Many fasteners are bored completely through the housing.
These fasteners must have thread sealant applied to the threads.
If oil leakage is observed at the PTO covers, replace the PTO cover gaskets and thoroughly clean the fasteners and their mating threads before reinstalling.
CAUTION!
Over-torquing a transmission output yoke retaining nut can cause output shaft bearing failure. Using a 1-inch air gun to tighten yoke retaining nuts should be avoided, although it is all right to remove the nut using this tool.
Many fasteners used to couple flanges and manifolds to the transmission are bored completely through the housing. These fasteners must have thread sealant applied to the threads. If oil leakage is observed at the PTO covers, replace the PTO cover gaskets and thoroughly clean the fasteners and their mating threads before reinstalling.

18. Shop Talk
Always check for a plugged transmission breather when identifying the cause of a transmission oil leak.
When transmission oil is raised from cold to operating temperatures, it expands to occupy a greater volume. If the breather is plugged, this can cause seal failure.
Shop Talk
Always check for a plugged transmission breather when identifying the cause of a transmission oil leak. When transmission oil is raised from cold to operating temperatures, it expands to occupy a greater volume. If the breather is plugged, this can cause seal failure.

19. Rear Seal Replacement REAR SEAL REPLACEMENT
If your troubleshooting has determined that the rear main oil seal is leaking, the end yoke has to be removed and the seal and slinger replaced. Check the yoke for signs of wear and damage (Figure 16–4). Pay special attention to the yoke seal surface. Any wear beyond normal polishing will require the yoke to be replaced or re-sleeved. There should be no rust, burrs, nicks, or grooves on the seal surface.

20. Shop Talk
Do not attempt to repair a visibly worn or damaged yoke by polishing it with crocus cloth.
Minor scratches can either track oil under the seal or draw in contaminants.

21. Caution Do not over-torque the yoke nut, which can damage the bearing.
Do not perform this operation using a 1-inch air gun.

22. Shop Talk
Wear rings that increase the original yoke diameter can cause the new seal to wear more rapidly due to increased seal lip pressure.

23. Transmission Troubleshooting Guidelines
See Table 16-2 on pages of the textbook.

24. Towing Precautions TOWING PRECAUTIONS
Trucks must be towed properly to prevent damage to the transmission and other drivetrain components as well as the frame. When towing a truck with a disabled transmission or other problem, standard transmissions require rotation of the main box countershaft and mainshaft gears to provide adequate lubrication. These gears do not rotate when the vehicle is towed with the rear wheels on the ground and the drivetrain connected. Under these conditions the mainshaft can be driven at high speed by the rear wheels. Without lubrication, it will be rapidly destroyed. You should note that coasting with the transmission in neutral can produce the same damage. The procedure to observe when towing should be as follows: 1. Pull the axle shafts or disconnect the driveline. 2. The recommended method of towing a truck is to use a rigid tow bar and connect it to the front tow hook or pin (Figure 16–11A). This prevents vehicle and frame damage and can be used with a vehicle that is loaded or unloaded. If you are using a wrecker without a tow bar, you can use the alternate method shown in Figure 16–11B. Place the lift bar cradle under the front axle and raise the truck for towing. 3. Tow the truck with its drive wheels off the ground (Figure 16–12) if it is impractical to disconnect the axle shafts or driveline.

25. Caution When the driveline or axle shafts are reinstalled:
The axle nuts must be tightened to the correct torques (Refer to the specific service manual for the correct torque values.)
The axle shafts properly installed (RH and LH)
The drive shafts properly phased
CAUTION!
When the driveline or axle shafts are reinstalled, the axle nuts must be tightened to the correct torques, the axle shafts properly installed (RH and LH), and the drive shafts properly phased. Refer to the specific service manual for the correct torque values.

26. General Transmission Removal Practices
Caution
Ensure that the transmission does not hang by the input shaft in the pilot bearing bore in the flywheel.
The clutch assembly, pilot bearing, and input shaft can be damaged if the transmission is supported by the input shaft.

27. Shop Talk
Engine torsionals refers to the frequency of torsional pulses delivered to the drivetrain as the force of each cylinder power stroke is unloaded into the crankshaft.
Because of today’s practice of managing engines at slower speeds and higher torque to produce better fuel economy, lower frequency torsionals are produced and this has caused some transmission failures.

28. Analysis of Bearing Failures
Fretting
The bearing outer race can pick up the machining pattern of the bearing bore.
It can be mistakenly diagnosed as one that has spun in the bore.
Contamination
Scoring, scratching, and pitting of bearing contact surfaces identify contamination failures.
It is caused by very fine particles suspended in the lubricant or by the use of older EP (extreme pressure) oils.
Analysis of Bearing Failures
We will now take a more detailed look at why transmission bearings fail.
Dirt. More than 90 percent of transmission bearing failures are caused by abrasive dirt. Dirt usually enters the bearings during assembly. Research by one major truck manufacturer concludes that this is why a reconditioned transmission unit has less than half the service life expectancy compared with a new one. Dirt can also enter through the seals or breather, or even from using dirty containers to add or change lubricant. Dirt in a transmission because of poor assembly practices is avoidable so make a practice of working clean. Softer material such as grain powder, smoke particulate, and light dust forms an abrasive paste within the bearings themselves. The rolling action of the bearing entraps the abrasives, which now work like lapping paste, eroding the hard surfacing. As bearings wear they become noisy. The abrasive action tends to increase rapidly as ground steel particles from the bearing hard-surfacing adds to the abrasives. Hard, coarser materials can enter the transmission during assembly from hammers, drifts, or power chisels. These materials can also be produced from within the transmission due to raking teeth, causing minute cuttings. These cuttings mixed with the lube produce small indentations in the critical contact areas of bearings and gear teeth.
Fatigue. Bearing fatigue is characterized by flaking or spalling of the bearing race. It is a metallurgical failure of the bearing that can be caused by old age or a manufacturing problem. Spalling is granular weakening of the hardened surface steel that causes it to flake away from the race. Because of their rough surfaces, spalled bearings will run noisy and produce vibration. Normal fatigue failure occurs when bearing service life is at an end and the bearing hard surfacing appears to be evenly worn through into the base metal below it. All bearings will eventually succumb to fatigue failure.
Lubrication failures. Bearing failures due to poor lubrication are characterized by discoloration, spalling, and sometimes bearing break-up. Failures can result from low oil level, contaminated lube, improper grade oil, and mixing of incompatible oil types. The use of additives falls into the last category. Lubrication failures are avoidable so ensure that PM practices are adhered to.
Brinelling. A brinelling condition (Figure 16–13) can be identified as tiny indentations high on the shoulder or in the valley of the bearing race. It can be caused by improper bearing installation or removal. Driving or pressing unevenly on a bearing can fractionally twist it, meaning that any force absorbed by the bearing is not distributed evenly by the race. This type of damage can be avoided by using correct drivers or pullers.
Fretting. Sometimes the bearing outer race can pick up the machining pattern of the bearing bore as a result of vibration. This action is called fretting (Figure 16–14). A fretted bearing can be mistakenly diagnosed as one that has spun in the bore. Fretting in itself does not require replacement of the bearing.
Contamination. Scoring, scratching, and pitting of bearing contact surfaces identify contamination failures. Contamination is caused by very fine particles suspended in the lubricant or by the use of older EP (extreme pressure) oils. This type of lube contamination will result in abrasive action and polishing of the bearing contact surfaces, which can significantly shorten the life of the bearing.

29. Shop Talk
Store new bearings in their shipping wrappers until ready for use.
Used bearings should be cleaned in solvent, lubricated, and wrapped in greasy paper until ready for installation.

30. Timing Transmissions
Multiple countershaft transmissions must be timed during assembly.
Timing ensures that the countershaft gears contact their mating mainshaft gears in phase to properly distribute the torque load.
When timing a transmission, follow the OEM procedure.
In the typical truck transmission used as an example in this chapter:
In the main section, it is necessary to time only the drive gear set.
In the auxiliary section, depending on the model, only the low range, deep reduction, or splitter gear sets have to be timed.

31. Timing the Front Section (1 of 2)
Before placing each countershaft assembly into the housing, mark the tooth located directly over the keyway of the countershaft drive gear.
In many transmissions, you might find that this tooth is stamped with an “O” to identify it.
Mark any two adjacent teeth on the main drive gear.
Timing the Front Section
Before reassembling the front section of the transmission, the drive gears of the mainshaft and the countershafts must be marked in the following way:
Before placing each countershaft assembly into the housing, mark the tooth located directly over the keyway of the countershaft drive gear, as shown in Figure 16–15A. In many transmissions, you might find that this tooth is stamped with an “O” to identify it.
Mark any two adjacent teeth on the main drive gear.
Mark the two adjacent teeth located directly opposite the first set marked on the main drive gear. As shown in Figure 16–15B, there should be an equal number of unmarked gear teeth on each side between the marked teeth.
After the mainshaft and countershaft are installed into the housing, the marked teeth should be meshed exactly as shown in Figure 16–16.

32. Timing the Front Section (2 of 2)
Mark the two adjacent teeth located directly opposite the first set marked on the main drive gear.
There should be an equal number of unmarked gear teeth on each side between the marked teeth.
After the mainshaft and countershaft are installed into the housing, the marked teeth should be meshed exactly as shown.
Timing the Front Section
Before reassembling the front section of the transmission, the drive gears of the mainshaft and the countershafts must be marked in the following way:
Before placing each countershaft assembly into the housing, mark the tooth located directly over the keyway of the countershaft drive gear, as shown in Figure 16–15A. In many transmissions, you might find that this tooth is stamped with an “O” to identify it.
Mark any two adjacent teeth on the main drive gear.
Mark the two adjacent teeth located directly opposite the first set marked on the main drive gear. As shown in Figure 16–15B, there should be an equal number of unmarked gear teeth on each side between the marked teeth.
After the mainshaft and countershaft are installed into the housing, the marked teeth should be meshed exactly as shown in Figure 16–16.

33. Timing the Auxiliary Section (1 of 2)
The specific gears on the mainshaft and countershafts that must be marked differ, depending on the auxiliary gearbox design.
Mark any two adjacent teeth on the mainshaft gear of the set to be timed.
Then mark the two adjacent teeth located directly opposite the first set marked.
Timing the Auxiliary Section
The gears in the auxiliary section must also be timed. The specific gears on the mainshaft and countershafts that must be marked differ, depending on the auxiliary gearbox design. A general procedure is as follows: 1. Mark any two adjacent teeth on the mainshaft gear of the set to be timed. Then mark the two adjacent teeth located directly opposite the first set marked, as shown in Figure 16–15B. 2. Before placing each auxiliary countershaft assembly into the housing, mark the tooth stamped with an “O” on gear to mate with timed the mainshaft gear, as shown in Figure 16–15A. 3. Install the mainshaft gear in position on the range mainshaft or output shaft. 4. Place the auxiliary countershaft assemblies into position and mesh the marked teeth of mating countershaft gears with the marked teeth of the mainshaft gear, as shown in Figure 16– Fully seat the rear bearings on each countershaft to complete the installation.

34. Timing the Auxiliary Section (2 of 2)
Mark the tooth stamped with an “O” on gear to mate with timed the mainshaft gear.
Install the mainshaft gear in position on the range mainshaft or output shaft.
Place the auxiliary countershaft assemblies into position and mesh the marked teeth of mating countershaft gears with the marked teeth of the mainshaft gear.
Fully seat the rear bearings on each countershaft to complete the installation.
Timing the Auxiliary Section
The gears in the auxiliary section must also be timed. The specific gears on the mainshaft and countershafts that must be marked differ, depending on the auxiliary gearbox design. A general procedure is as follows:
Mark any two adjacent teeth on the mainshaft gear of the set to be timed. Then mark the two adjacent teeth located directly opposite the first set marked, as shown in Figure 16–15B.
Before placing each auxiliary countershaft assembly into the housing, mark the tooth stamped with an “O” on gear to mate with timed the mainshaft gear, as shown in Figure 16–15A.
Install the mainshaft gear in position on the range mainshaft or output shaft.
Place the auxiliary countershaft assemblies into position and mesh the marked teeth of mating countershaft gears with the marked teeth of the mainshaft gear, as shown in Figure 16– Fully seat the rear bearings on each countershaft to complete the installation.

35. Summary (1 of 6)
Scheduled lubrication services are key to a good transmission maintenance program.
Standard transmissions depend on splash lubrication, meaning that some of the rotating components contact, pick up, and circulate oil from the oil in the sump.
Maintaining the correct oil level is critical for splash lubrication to be effective.

36. Summary (2 of 6)
Only lubricants recommended by the transmission manufacturer should be used in a transmission.
These could be either gear or engine oils.
It is usually recommended that the first oil change be performed shortly after the transmission enters service, often between 3,000 and 5,000 miles of operation in a linehaul application, or less in vocational service.

37. Summary (3 of 6)
In general linehaul application, it is good practice to schedule a transmission oil change from 50,000 to 100,000 miles of service.
Good preventive maintenance (PM) lowers the incidence of breakdowns, minimizes downtime, and reduces the cost of repairs.

38. Summary (4 of 6)
Leakage in transmission rear seals is a relatively common problem in truck transmissions, but one that is easily repaired.
When diagnosing transmission complaints, it is important that you confirm that the transmission is the actual cause of the problem before removing it for repair.

39. Summary (5 of 6)
When disassembling a transmission, each component should be carefully inspected for abnormal wear and damage.
Components that are not reusable should be ordered after disassembly, not discovered during reassembly.
Ensure that a cause of failure is determined before reassembly, or the failure is likely to recur within a short period.

40. Summary (6 of 6)
Bearing failures occur because of dirt contamination and poor lubrication.
More than 90 percent of bearing failures are caused by dirt.
Cleanliness is critical when repairing and servicing standard transmissions.