1. Heavy-Duty Truck Axle Service and Repair
Chapter 24
Heavy-Duty Truck
Axle Service and Repair

2. Objectives (1 of 2)
Describe the lubrication requirements of truck and trailer dead axles.
Outline the lubrication service procedures required for truck drive axle assemblies.
Perform some basic level troubleshooting on differential carrier gearing.
Outline the procedure required to disassemble a differential carrier.

3. Objectives (2 of 2) Disassemble a power divider unit.
Perform failure analysis on power divider and differential carrier components.
Reassemble power divider and differential carrier assemblies.

4. Axle Fill and Drain Plugs

5. Axle Lube Viscosity
See Table 24-1 on page 706 in the textbook.

6. Shop Talk
Draining lubricants when warm ensures that contaminants are still suspended and also reduces drain time.

7. Power Divider Oil Fill and Drain Plugs

8. Checking the Lube Level

9. Proper Lubricant Levels

10. Caution
On most drive axles, there is no external visual means of checking lubricant level in the wheel end, so the importance of making sure the drive axle lubricant level is correct cannot be overemphasized.
Raising each side of an axle with a jack ensures oil fills the wheel-end hub cavity.
Make a final check of the differential carrier oil level after tilting the axle from both sides.

11. Wheel Hub Lube Cavity

12. Differential Carrier Identification

13. Axle Identification

14. Crown Gear and Pinion Identification

15. Failure Analysis Shock load Fatigue Spinout Faulty lubrication
Normal wear

16. Caution
Most driver-abuse generated failures do not cause an instantaneous equipment failure.
The equipment failure can take place some time after the driving incident that generated it.
This is important to remember when attempting to attribute blame in fleets that do not assign drivers dedicated trucks.

17. Fracture Patterns

18. Surface Failure Patterns

19. Torsional Failure

20. Bending Failure Patterns

21. Spinout

22. Always Support the Truck With Axle Stands

23. Shop Talk
You sometimes have to use more force to pop axle shafts than can be delivered using a drift and 4-lb. hammer.
When this method does not work, use a 16-lb. sledgehammer directly on center of the axle shaft flange; use a ¼ swing of the sledgehammer, letting the weight of the hammer do all of the work.

24. Caution
Most of the weight of a differential carrier assembly is on the inboard side of its mounting flange.
Ensure that the assembly is properly fastened to the jacking device and that your body is never positioned under the carrier.

25. Thrust Screw

26. Marking the Carrier Components

27. Lock Plate and Adjusting Rings

28. Removing the Bearing Cap and Adjusting Ring

29. Differential Spider Gears

30. Drill and Punch Out Rivets

31. Caution
Do not remove the rivet heads or rivets with a chisel and hammer because this can damage the flange case half or enlarge the rivet holes, resulting in loose rivets.

32. Remove the Ring Gear

33. Removing the Pinion Flange or Yoke

34. Bearing Cage Removal

35. Removing Pinion with Bearing Cage

36. Pressing the Drive Pinion from the Bearing Cage

37. Pinion Bearing Removal

38. Spigot Bearing

39. Removing Power Divider

40. Power Divider Dowel Pins

41. Power Divider Assembly

42. Interaxle Differential

43. Measuring End Play

44. Pinion Bearing Cage Assembly

45. Check Pinion Bearing Preload

46. A Tool to Check Rolling Resistance

47. Checking Rolling Resistance

48. Drive Pinion Depth Controlled by Shim Pack Thickness

49. Pinion Cone Variation Number

50. Determining Shim Pack Thickness
See Figure on page 732 of the textbook.

51. Checking Crown Gear Runout

52. Check Crown Gear Backlash

53. Adjustments to Increase Backlash

54. Adjustments to Decrease Backlash

55. Crown Gear Tooth Nomenclature

56. Checking Tooth Contact

57. Correct Contact Pattern for Used Gearing

58. Incorrect Pinion Position

59. Incorrect Backlash Patterns

60. Adjusting the Thrust Screw

61. Summary (1 of 6)
Adhering to OEM-recommended lubrication schedules is the key to ensuring the longest service life from both drive and dead axles.
Knowing the correct procedure to check lubricant level is essential.
The level is correct when lubricant is exactly level with the bottom of the fill hole.

62. Summary (2 of 6)
Because most OEMs approve of the use of synthetic lubricants in final drive carriers, lubrication drain schedules have been greatly increased in recent years.
Drain schedules are determined by the actual lubricant used and the type of application to which the vehicle is subjected.
Servicing of axles on heavy-duty trucks consists of routine inspection, lubrication, cleaning, and, when required, troubleshooting and component overhaul.

63. Summary (3 of 6)
Failure analysis is required to prevent recurrent failures.
Drive axle carrier components usually fail for one of the following reasons:
Shock load
Fatigue
Spinout
Lubrication problems
Normal wear

64. Summary (4 of 6)
Most differential carriers are replaced as rebuilt/exchange units, so the role of the technician is, more often than not, to diagnose the problem and then, if necessary, replace the defective assembly as a unit.
The technician who has disassembled and reassembled differential carriers should find troubleshooting procedures easier to follow.

65. Summary (5 of 6)
Follow the OEM procedure when disassembling differential carriers.
Taking a few moments to measure shim packs and gear tooth contact patterns on disassembly can save considerable time when reassembling the carrier.
A crown and pinion gearset often can be reused when rebuilding a differential carrier. Make sure you inspect it properly on disassembly.

66. Summary (6 of 6)
Crown and pinion gearsets are always replaced as a matched pair during a rebuild.
When setting crown and pinion backlash, it is increased by moving the crown gear away from the drive pinion, and decreased by moving the crown gear toward the drive pinion.