Chevrolet Silverado / GMC Sierra. Service manual — part 1477

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 for the drive pinion bearings 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 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 bearing cups into the

axle housing.

5. Insert one BENT 1.016 mm (0.040 in) thick service shim into the right side axle housing.

Side the differential assembly towards the bent service shim in order to hold the shim in
place.

6. While holding the differential assembly against the bent service shim, install one 4.318 mm

(0.170 in) thick service spacer into the left side axle housing.

7. Move the differential assembly to the right until the ring gear contacts the drive pinion.

Once the ring gear contacts the drive pinion, continue to move the ring gear towards the
drive pinion to until all backlash is removed.

8. While holding the ring gear against the drive pinion, insert progressively larger service

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 service 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 service spacers instead.

IMPORTANT: Before installation of the case assembly, 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.

2008 Chevrolet Silverado 1500

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

shims between the service spacer and the differential side bearing cup until a moderate
resistance can be felt.

9. Once the largest service shim has been determined, measure the thickness of the shim using a

micrometer. Measure the service shim in 3 locations. Calculate the average of the 3
measurements. Use the average as the thickness for the shim. Record the measurement.

10. Install the service shim that was just measured back into the left side of the axle housing.

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

11. Remove the BENT shim from the right side of the axle housing.

12. Insert one 4.318 mm (0.170 in) thick service spacer into the right side axle housing.

13. Move the differential assembly towards the left side of the axle housing. While holding the

differential assembly against the left side shim pack, insert progressively larger service shims
between the service spacer and the differential side bearing cup until a moderate resistance
can be felt.

14. Once the largest service shim has been determined, measure the thickness of the shim using a

micrometer. Verify the thickness of the service shim. Measure the service shim in 3
locations. Calculate the average of the 3 measurements. Use the average as the thickness for
the shim. Record the measurement.

15. In order to preload the differential side bearing and set the initial backlash to approximately

0.127 mm (0.005 in), adjust the thickness of left and right side shims by doing the following:

1. Subtract 0.152 mm (0.006 in) from the measurement recorded for the left side shim in

step 9. Record the measurement.

2. Add 0.356 mm (0.014 in) to the measurement recorded for the right side shim in step

14.

16. Select the correct service shim thickness for each side corresponding to the measurements

determined above. Using a micrometer, verify the thickness of the service shim. Measure the
service shim in 3 locations. Calculate the average of the 3 measurements. Use the average as
the thickness for the shim.

17. Install the left side service shim into the axle housing. The service shim must be installed

between the service spacer and the differential side bearing cup.

18. Move the differential assembly towards the left side of the axle housing.

19. 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.

NOTE:

Refer to Fastener Notice .

2008 Chevrolet Silverado 1500

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

20. Install the differential bearing caps and bolts.

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

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

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

pound torque wrench.

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

23. Calculate the differential side bearing preload by subtracting the drive pinion preload,

measured in Step 2, from the drive pinion and the differential case bearing preload,
measured in Step 23. 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).

24. 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.

25. Once the differential side bearing preload is within specifications, measure the backlash

between the ring gear and the drive pinion 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).

26. Once backlash and differential side bearing preload is within specifications, 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.

DIFFERENTIAL CARRIER BEARING PRELOAD ADJUSTMENT (9.5, AND 9.5LD INCH AXLES
AXLES)

Tools Required

J 22779 Side Bearing Backlash Gage. See Special Tools.

J 24429 Side Bearing Backlash Spanner. See Special Tools.

Adjustment

IMPORTANT:

Ensure that the side bearing surfaces in the axle housing are
clean and free of burrs. If the original bearings are to be

2008 Chevrolet Silverado 1500

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

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 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.

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.

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.

CAUTION: To prevent personal injury and/or component damage,

support the differential case when removing the case
from the axle housing. If the case is not supported, the
differential case could fall and cause personal injury or
damage to the differential case.

IMPORTANT: Do not force the ring gear into contact with the drive pinion.

2008 Chevrolet Silverado 1500

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