Chevrolet Silverado / GMC Sierra. Service manual — part 1476

21. Tighten differential bearing adjuster nut lock bolts.

Tighten: Tighten the differential bearing adjuster nut lock bolts to 27 N.m (20 lb ft).

22. Measure the ring gear to pinion backlash and adjust, if necessary. Refer to Backlash

Adjustment (8.6 Inch Axle) or Backlash Adjustment (10.5, 11.5 Inch Axles) or
Backlash Adjustment (9.5 LD Axle).

DIFFERENTIAL CARRIER BEARING PRELOAD ADJUSTMENT (8.6 INCH AXLE)

Wedge Method

Tools Required

J 22779 Side Bearing Backlash Gage. See Special Tools.

J 25588 Side Bearing Shim Installer. See Special Tools.

Adjustment

1. Install the drive pinion, if necessary. Refer to Drive Pinion and Ring Gear Replacement

(8.6, 9.5/9.5LD, and 11.5 Inch Axles) or Drive Pinion and Ring Gear Replacement
(10.5 Inch Axle).

2. Measure the rotating torque of the drive pinion using an inch-pound torque wrench. Record

the measurement.

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.

IMPORTANT:

The differential side bearing preload adjustment must be
completed before the backlash adjustment can be started.

In order to maintain the original backlash, adjust the
differential case side bearing preload by changing the
thickness of the left and the right side shim packs equally.

Measure the service shims and the spacers one at a time.
Add the measurements together in order to obtain the total
thickness of the left or the right side shim pack.

Do not use or reuse the original cast iron production shims.
Use service shims and spacers instead.

2008 Chevrolet Silverado 1500

2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

3. If the rotating torque for the drive pinion bearings is not within specifications, adjust as

necessary. Refer to Drive Pinion and Ring Gear Replacement (8.6, 9.5/9.5LD, and 11.5
Inch Axles) or Drive Pinion and Ring Gear Replacement (10.5 Inch Axle).

4. Install the differential assembly with the differential side bearings and differential side

bearing cups into the axle housing.

5. Insert one 4.318 mm (0.170 in) thick service spacer into the left side of the axle housing.

6. Side the differential assembly towards the service spacer in order to hold the spacer in

place.

7. Install the J 22779 into the right side of the axle housing. See Special Tools.

The J 22779 must be installed between the service spacer and the differential side bearing
cup. See Special Tools.

8. Tighten the knob on the J 22779 until there is moderate drag when the J 22779 is moved.

See Special Tools.

9. Remove the J 22779 . See Special Tools.

10. Remove the service spacer.

11. Using a micrometer, measure the thickness of the service spacer. Record the measurement.

12. Using a micrometer, measure the thickness of the J 22779 in 3 locations. See Special Tools.

Calculate the average of the 3 measurements. Record the measurement.

13. Add the thickness of the service spacer, measured in step 11 to the average thickness of the J

22779 , measured in step 12. See Special Tools. The resulting value is the total service shim
thickness without preload for the axle.

14. Insert one BENT 1.016 mm (0.040 in) service shim between the right side differential side

bearing cup and the axle housing. The service shim must be installed between the service
spacer and the differential side bearing cup.

15. Install the J 22779 into the left side of the axle housing. See Special Tools. The J 22779

IMPORTANT: Before installation of the differential assembly, ensure that

the differential side bearing surfaces in the axle housing are
clean and free of burrs. If the original differential side
bearings are to be reused, the original differential side
bearing cups must also be used.

IMPORTANT: Over-tightening of the J 22779 may spread the housing and

result in incorrect shim selection. See Special Tools.

2008 Chevrolet Silverado 1500

2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

must be installed between the service spacer and the differential side bearing cup. See
Special Tools.

16. While rotating the ring gear back and forth, tighten the knob on the J 22779 until there is

approximately 0. See Special Tools.025-0.051 mm (0.001-0.002 in) of backlash between
the ring gear and the drive pinion.

17. Once the correct amount of backlash is obtained, remove the J 22779 . See Special Tools.

18. Remove the differential assembly with the differential side bearings and the differential side

bearing cups.

19. Remove the BENT service shim.

20. Using a micrometer, measure the thickness of the J 22779 in 3 locations. See Special Tools.

Calculate the average of the 3 measurements. This value is the left side service shim
thickness without preload.

21. In order to determine the right side service shim thickness, subtract the service shim

thickness for the left side of the axle, calculated in step 20, from the total service shim
thickness, calculated in step 13. This value is the service shim thickness for the right side of
the axle without preload.

22. In order to preload of the differential side bearings and set the backlash to approximately

0.127-0.223 mm (0.005-0.009 in), take the value determined in step 21 and add 0.203 mm
(0.008 in) service shim thickness to this amount.

23. Assemble the left side shim pack using one 4.318 mm (0.170 in) service spacer and the

appropriate amount of service shims equaling the thickness determined in step 20. Measure
the service spacer and the service shims separately. Add the measurements together in order
to determine the total shim pack thickness.

24. Assemble the right side shim pack using one 4.318 mm (0.170 in) service spacer and the

appropriate amount of service shims equaling the thickness determined in step 22. Measure
the service spacer and the service shims separately. Add the measurements together in order
to determine the total shim pack thickness.

25. Install the differential assembly with the differential side bearings and the differential side

bearing cups.

26. Install the left side service spacer and service shim into the axle housing. The service shim

must be installed between the service spacer and the differential side bearing cup.

27. Install the right side service spacer between the axle housing and the differential side

bearing cup.

28. Install the right side service shim into the axle housing using the J 25588 , if necessary. See

Special Tools. The service shim must be installed between the service spacer and the
differential side bearing cup.

2008 Chevrolet Silverado 1500

2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

29. Install the differential bearing caps and the bolts.

Tighten: Tighten the differential bearing cap bolts to 75 N.m (55 lb ft).

30. Rotate the pinion several times to ensure the drive pinion and differential side bearings have

seated.

31. Measure the rotating torque of the drive pinion and differential side bearings using an inch-

pound torque wrench. Record the measurement.

Specification: 0.57-1.13 N.m (5-10 lb in) greater than the rotating torque of the drive
pinion measured earlier.

32. 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 31. Multiply the value obtained by the axle ratio.

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

33. If the differential side bearing preload is not within specifications, add or subtract shim

thickness equally from each shim pack as necessary in order to increase/decrease the side
bearing preload.

34. Once the differential side bearing preload is correct, measure the backlash and adjust, if

necessary. Refer to Backlash Adjustment (8.6 Inch Axle) or Backlash Adjustment
(10.5, 11.5 Inch Axles) or Backlash Adjustment (9.5 LD Axle).

35. Once the differential side bearing preload and backlash is correct, perform a gear tooth

contact pattern check in order to ensure proper alignment between the ring and pinion gears.
Refer to Gear Tooth Contact Pattern Inspection.

Shim Method

Tools Required

J 25588 Side Bearing Shim Installer. See Special Tools.

Adjsutment

NOTE:

Refer to Fastener Notice .

IMPORTANT:

The differential side bearings must have preload before the
backlash adjustment can be started.

2008 Chevrolet Silverado 1500

2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado