Chevrolet Silverado / GMC Sierra. Service manual — part 1481

2. Remove the differential case assembly with the bearing cups and the shims.

Mark the bearing cups and the shims left or right.

3. Measure the thickness of left side shim pack.

Measure the production shim or the shim and service spacer in 3 locations.

Measure each shim separately.

4. Calculate the average of the 3 measurements for each shim.

Add the average of each of the shim measurements together.

Record the measurement. This is the thickness for the left side shim pack.

5. Assemble a new left side shim pack by increasing the appropriate amount of thickness

to the original left side shim pack. If the original shim is cast iron production shim,
assemble the shim pack using a service spacer and service shims. For example, to
increase the backlash by 0.05 mm (0.002 in), add 0.10 mm (0.004 in) of thickness to
the left side shim pack.

6. Measure the thickness of right side shim pack.

Measure the shim or the shim and service spacer in 3 locations.

Measure each shim separately.

7. Calculate the average of the 3 measurements for each shim.

Add the average of each of the shim measurements together.

Record the measurement. This is the thickness for the right side shim pack.

8. Assemble a new right side shim pack by decreasing the appropriate amount of

thickness to the original right side shim pack. If the original shim is cast iron
production shim, assemble the shim pack using a service spacer and service shims. For
example, to decrease the backlash by 0.05 mm (0.002 in), remove 0.10 mm (0.004 in)
of thickness to the right side shim pack.

11. Install the differential case assembly with the bearing cups.

12. Install the left side service spacer between the axle housing and the differential case.

2008 Chevrolet Silverado 1500

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

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

Fig. 264: Installing Left Side Service Shim Using J 25588
Courtesy of GENERAL MOTORS CORP.

14. Install the left side service shim or shims using the J 25588 , if necessary. See Special

Tools.

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

15. Install the right side service shim or shims using the J 25588 , if necessary. See Special

Tools.

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

2008 Chevrolet Silverado 1500

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

16. Install the bearing caps and bolts.

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

17. Recheck the backlash and adjust, if necessary.

18. Once 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.

BACKLASH ADJUSTMENT (10.5, 11.5 INCH AXLES)

Special Tools

J 8001 Dial Indicator Set

J 24429 Side Bearing Backlash Spanner. See Special Tools.

J 25025 Guide Pins. See Special Tools.

Adjustment

NOTE:

Refer to Fastener Notice .

IMPORTANT:

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 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.

2008 Chevrolet Silverado 1500

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

Fig. 265: Measuring Pinion Rotating Torque
Courtesy of GENERAL MOTORS CORP.

1. Measure the rotating torque of the drive pinion and differential assembly using an inch-

pound torque wrench.

Specification: The rotating torque of the drive pinion and differential assembly should be
2.3-4.5 N.m (20-40 lb in) for new bearings or 1.7-3.4 N.m (15-30 lb in) for used bearings.

2. If the rotating torque is too low, tighten the differential bearing adjuster nuts in 1 slot

increments until the specified rotating torque is obtained.

3. If the rotating torque is too high, loosen the differential bearing adjuster nuts in 1 slot

increments until the specified rotating torque is obtained.

4. If the specification for the rotating torque of the drive pinion and differential assembly

cannot be obtained by adjusting the differential bearing adjuster nut, remove the differential
assembly, measure the rotating torque of the drive pinion and adjust as necessary. Refer to
Differential Replacement (8.6, 9.5/9.5LD Inch Axles) or Differential Replacement
(10.5 Inch, 11.5 Inch Axle) and Drive Pinion Bearings Replacement (8.6, 9.5, 11.5
Inch Axle) or Drive Pinion Bearings Replacement (10.5 Inch Axle).

2008 Chevrolet Silverado 1500

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