Backlash Adjustment (G86)

Special Tools J-25025-7A Dial Indicator Mounting Post J-8001 Dial Indicator Set Equivalent regional tools: Special Tools Procedure

Note

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.

1. Install the J-25025-7A Dial Indicator Mounting Post and the J-8001 Dial Indicator Set to the axle housing.

Note

Preload the dial of the J-8001 Dial Indicator Set approximately ¾ of a turn and zero the gauge.

2. Set the J-8001 Dial Indicator Set so that the stem is aligned with the gear rotation and square to the tooth angle.
3. Hold the drive pinion stationary, move the ring gear back and forth.
4. Repeat the measuring procedure at eight points around the ring gear.
5. The difference between the backlash at all of the measuring points should not vary by more than 0.05 mm (0.002 in).
6. 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.
7. If the difference between all the measuring points is within specifications, the backlash at the minimum lash point measured should be within the specification. Axle Preload and Backlash Specifications
8. If the backlash is too small, increase the backlash using the following procedure:

Note

Mark the bearing cups and the shims left or right. 8.1. Remove the differential case assembly with the bearing cups and the shims. 8.2. Measure the production shim or the shim and service spacer in 3 locations. 8.3. Measure each shim separately. 8.4. Measure the thickness of left side shim pack. 8.5. Add the average of each of the shim measurements together. 8.6. Record the measurement. This is the thickness for the left side shim pack 8.7. Calculate the average of the 3 measurements for each shim.

Note

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), remove 0.10 mm (0.004 in) of thickness from the left side shim pack. 8.8. Assemble a new left side shim pack by decreasing the appropriate amount of thickness from the original left side shim pack. 8.9. Measure the thickness of right side shim or the shim and service spacer in 3 locations. 8.10. Measure each shim separately. 8.11. Measure the thickness of right side shim pack. 8.12. Add the average of each of the shim measurements together. 8.13. Record the measurement. This is the thickness for the right side shim pack. 8.14. Calculate the average of the 3 measurements for each shim.

Note

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 from the right side shim pack. 8.15. Assemble a new right side shim pack by increasing the appropriate amount of thickness to the original right side shim pack.

9. If the backlash is too large, decrease the backlash using the following procedure:

Note

Mark the bearing cups and the shims left or right. 9.1. Remove the differential case assembly with the bearing cups and the shims. 9.2. Measure the production shim or the shim and service spacer in 3 locations. 9.3. Measure each shim separately. 9.4. Measure the thickness of left side shim pack. 9.5. Add the average of each of the shim measurements together. 9.6. Record the measurement. This is the thickness for the left side shim pack. 9.7. Calculate the average of the 3 measurements for each shim.

Note

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), add 0.10 mm (0.004 in) of thickness from the left side shim pack. 9.8. Assemble a new left side shim pack by increasing the appropriate amount of thickness to the original left side shim pack. 9.9. Measure the shim or the shim and service spacer in 3 locations. 9.10. Measure each shim separately. 9.11. Measure the thickness of right side shim pack. 9.12. Add the average of each of the shim measurements together. 9.13. Record the measurement. This is the thickness for the right side shim pack. 9.14. Calculate the average of the 3 measurements for each shim.

Note

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 from the right side shim pack. 9.15. Assemble a new right side shim pack by decreasing the appropriate amount of thickness to the original right side shim pack.

Note

The service spacers must be installed between the service shim (s) and the axle housing.

Note

A dead blow hammer can be used to help seat the differential and shim.

10. Install the differential, spacer, and shims.

Note

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

11. Recheck the backlash and adjust if necessary.
12. Return to the previous procedure and continue from appropriate step which linked to this procedure.