Adjustment Procedure

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Measure the rotating torque of the drive pinion and differential assembly. Refer to Differential Drive Pinion Gear Bearing Replacement (8.6, 9.5, 11.5 Inch Axle) or Differential Drive Pinion Gear Bearing Replacement (10.5 Inch Axle)

Fig 1: Measuring Ring Gear Backlash

Courtesy of GENERAL MOTORS CORP.

Install the J 25025: pins and the J 8001: indicator to the axle housing.

NOTE: Preload the dial of the J 8001-3 approximately 3/4 of a turn and zero the gauge.

Set the J 8001-3 so that the stem is aligned with the gear rotation and square to the tooth angle.
Hold the drive pinion stationary, move the ring gear back and forth.
Repeat the measuring procedure at eight points around the ring gear.
The difference between the backlash at all of the measuring points should not vary by more than 0.05 mm (0.002 in).
If the difference between the backlash at all of the measuring points varies by more than 0.05 mm (0.002 in), inspect for burrs, a distorted case flange or uneven bolting.
If the difference between all the measuring points is within specifications, the backlash at the minimum lash point measured should be 0.08-0.25 mm (0.003-0.010 in) with a preferred backlash of 0.13-0.18 mm (0.005-0.007 in).
If the backlash is not within specifications, remove the differential bearing adjuster nut retainer bolt and retainer.
Loosen, but DO NOT remove the bearing cap bolts.
Using the J 24429: spanner, loosen the differential bearing adjuster nut.
Remove the differential side bearing shim and measure the thickness of the shim.

NOTE: Increasing or decreasing the shim thickness by 0.05 mm (0.002 in) will change the backlash adjustment approximately 0.03 mm (0.001 in).

Calculate the average of the 3 measurements.

NOTE:

If the backlash is less than, select a smaller shim than the one that was removed. For example, to increase the backlash by 0.05 mm (0.002 in), select a shim that is 0.10 mm (0.004 in) thinner than the shim that was removed.
If the backlash is larger than, select a larger shim than the one that was removed. For example, to increase the backlash by 0.05 mm (0.002 in), select a shim that is 0.10 mm (0.004 in) thicker than the shim that was removed.

Install the selected shim.
Using the J 24429: spanner, tighten the differential bearing adjuster nut until the differential bearing adjuster nut is seated against the bearing cup.
With the differential bearing adjuster nut is seated against the differential bearing, use the J 24429: spanner tighten the differential bearing adjuster nut the following additional amounts.
- For used bearings, turn the differential adjuster nut an additional 2 slots.
- For new bearings, turn the differential adjuster nut an additional 3 slots.

CAUTION: Refer to Fastener Caution .

NOTE: Recheck the backlash following the steps above to verify that the backlash is within specifications.

Tighten the differential bearing cap bolts to 85 N.m (63 lb ft).
Install the differential bearing adjuster nut retainer.
Install the differential bearing adjuster nut retainer bolt and tighten to 26 N.m (19 lb ft).
Measure the drive pinion and differential case side bearing preload and adjust, if necessary following the steps above.
Once the backlash and bearing preload 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 .