Differential Side Bearing Preload Adjustment (9.5 Inch Axle)

Tools Required 

• J 8001  Dial Indicator Set
• J 22779  Side Bearing Backlash Gage
• J 24429  Side Bearing Backlash Spanner
• J 25025  Guide Pins

• Ensure that the side bearing surfaces in the axle housing are clean and free of burrs. If the original bearings are to be reused, the original bearing cups must also be used.
• The drive pinion bearing preload must be within specifications before the differential side bearing preload adjustment can be performed.
• The differential side bearings must be initially preloaded in order to determine the backlash of the gear set. After the backlash is set, the final bearing preload is set.

Fig 1: Measuring Drive Pinion Rotating Torque

Courtesy of GENERAL MOTORS CORP.

1. Remove the differential assembly, if necessary.
2. Measure the rotating torque of the drive pinion bearing using an inch-pound torque wrench.

   Specification 

   The rotating torque of the drive pinion should be 1.7-3.4 N.m (15-30 lb in) for new bearings or 1.1-2.3 N.m (10-20 lb in) for used bearings.

3. If the rotating torque of the drive pinion is less than 1.7 N.m (15 lb in) for new bearings or 1.1 N.m (10 lb in) for used bearings, tighten the pinion in small increments until the specified rotating torque is obtained.
4. If the rotating torque of the drive pinion is greater than 3.4 N.m (30 lb in) for new bearings or 2.3 N.m (20 lb in) for used bearings, remove the drive pinion and replace the collapsible spacer and re-install the drive pinion. Refer to Drive Pinion Bearings Replacement (8.6, 9.5, 11.5 Inch Axles)  or Drive Pinion Bearings Replacement (9.75 Inch Axle)  or Drive Pinion Bearings Replacement (10.5 Inch Axle) .
5. Install the differential assembly, if necessary.
6. Support the differential assembly in order to prevent the differential assembly from falling out of the axle housing.
   IMPORTANT: Do not force the ring gear into contact with the drive pinion.
7. Slide the differential case assembly towards the right side axle housing until the ring gear contacts the drive pinion.

   This is the ZERO backlash point.

   If the ZERO backlash cannot be obtained, turn the differential bearing adjuster nut into the axle housing using the J 24429  until the ring gear fully contacts the drive pinion to obtain the ZERO backlash.

8. While holding the ring gear against the pinion, turn the differential bearing adjuster nut out from the axle housing using the J 24429  until it contacts the differential side bearing.
9. Turn the adjuster nut out from the axle housing an additional 2 slots using the J 24429  in order to obtain the initial backlash adjustment.
10. Install the adjuster nut lock and the adjuster nut lock bolt.
11. Remove the left side differential bearing cap bolts.
12. Remove the left side differential bearing cap.
13. Install the J 22779  into the left side axle housing between the differential bearing bore and the differential bearing cup.
    IMPORTANT: Over-tightening may spread the axle housing and result in incorrect shim selection.
14. Tighten the knob of the J 22779  until there is moderate drag when the J 22779  is moved.
15. Remove the J 22779. 
16. Measure the J 22779  in 3 locations.
17. Calculate the average of the 3 measurements.

    The resulting value is the shim thickness required in order to set the initial backlash of the differential assembly.

18. Select a service shim of approximately the same thickness to install into the axle housing.

    Verify the thickness of the service shim using a micrometer.

19. Install the service shim into the axle housing between the differential bearing bore and the differential bearing cup.
20. Install the left side differential bearing cap.
21. Install the left side differential bearing cap bolts.

    Tighten the differential bearing cap bolts finger-tight. Do not torque the bolts at this time.

22. Remove the differential bearing adjuster nut lock bolt.
23. Remove the differential bearing adjuster nut lock.
24. Firmly tighten the differential bearing adjuster nut using the J 24429  in order to force the differential case assembly into solid contact with the service shim.
25. Rotate the pinion several times in order to seat the bearings.
26. Loosen the differential bearing adjuster nut using the J 24429  until the nut is free from the differential side bearing.
27. Tighten the differential bearing adjuster nut using the J 24429  until the differential bearing adjuster nut contacts the bearing.
28. Once the right differential bearing adjuster contacts the differential bearing, tighten the differential bearing adjuster nut using the J 24429  the following additional amounts:

    Tighten 

    • For new bearings, tighten the differential bearing adjuster nut an additional 3 slots.
    • For used bearings, tighten the differential bearing adjuster nut an additional 2 slots.
29. Install the right differential bearing adjuster nut lock.
30. Install the right differential bearing adjuster nut lock bolt.

    Do not torque the bolt at this time.

    NOTE: Refer to FASTENER NOTICE .
31. Tighten the bearing cap bolts.

    Tighten 

    Tighten the bearing cap bolts to 85 N.m (63 lb ft).

32. Tighten the differential bearing adjuster nut lock bolt.

    Tighten 

    Tighten the differential bearing adjuster nut lock bolt to 26 N.m (19 lb ft).

33. Measure the drive pinion and differential case side bearing preload using an inch-pound torque wrench.

    Rotate the pinion several times to ensure the bearings have seated.

    Specification 

    The rotating torque of the drive pinion and differential case bearings should be 3.9-6.2 N.m (30-55 lb in) for new bearings or 2.8-5.1 N.m (25-45 lb in) for used bearings.

    Record the measurement.

34. Calculate the differential side bearing preload by subtracting the drive pinion preload, measured in Step 2, from the drive pinion and differential case bearing preload, measured in Step 35.

    Multiply the value obtained by the axle ratio.

    Specification 

    The differential case side bearing preload should be 1.7-4.0 N.m (15-35 lb in).

35. If the differential case side bearing preload is not within specifications, increase or decrease the shim thickness as necessary in order to increase/decrease the side bearing preload.
36. Once the differential side bearing preload is correct, measure the drive pinion to differential assembly backlash and adjust, if necessary. Refer to Backlash Adjustment (All Except 9.75 Inch Axle)  or Backlash Adjustment (9.75 Inch Axle) .

    Differential side bearing shims are available in the following sizes:

    Shim Sizes 

    • 5.59 mm (0.220 in)
    • 5.64 mm (0.222 in)
    • 5.69 mm (0.224 in)
    • 5.74 mm (0.226 in)
    • 5.79 mm (0.228 in)
    • 5.84 mm (0.230 in)
    • 5.89 mm (0.232 in)
    • 5.94 mm (0.234 in)
    • 5.99 mm (0.236 in)
    • 6.05 mm (0.238 in)
    • 6.10 mm (0.240 in)
    • 6.15 mm (0.242 in)
    • 6.20 mm (0.244 in)
    • 6.25 mm (0.246 in)
    • 6.30 mm (0.248 in)
    • 6.35 mm (0.250 in)
    • 6.40 mm (0.252 in)
    • 6.45 mm (0.254 in)
    • 6.50 mm (0.256 in)
    • 6.55 mm (0.258 in)