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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 45 (Rear Drive Axle) >> Repair Instructions >> Backlash Adjustment (9.5 Inch Axle)

Backlash Adjustment (9.5 Inch Axle)

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Special Tools

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. After the backlash is set, the final bearing preload is set.
  • Mark the bearing caps left or right sides
  1. Measure the rotating torque of the drive pinion and differential assembly. Refer to Differential Drive Pinion Gear Bearing Replacement (10.5 Inch Axle) , or Differential Drive Pinion Gear Bearing Replacement (9.5 Inch Axle) .
  2. GM6946

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

    3. NOTE:

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

  3. Set the J 8001-3  indicator so that the stem is aligned with the gear rotation and square to the tooth angle.
  4. Hold the drive pinion stationary, move the ring gear back and forth.
  5. Repeat the measuring procedure at eight points around the ring gear.
  6. The difference between the backlash at all of the measuring points should not vary by more than 0.05 mm (0.002 in).
  7. 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.
  8. 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).
    9. 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).

  9. Calculate the average of the 3 measurements.
    10. 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 DECREASE 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.
  10. Install the selected shim.
    11. CAUTION:

    Refer to Fastener Caution .

  11. If the backlash is too small, increase the backlash using the following procedure:
    1. Remove the bearing cap bolts and the bearing caps.
      2. NOTE:

      Mark the bearing cups and the shims left or right.

    2. Remove the differential case assembly with the bearing cups and the shims.
      3. NOTE:
      • Measure the production shim or the shim and service spacer in 3 locations.
      • Measure each shim separately.
    3. Measure the thickness of left side shim pack.
      4. NOTE:
      • Add the average of each of the shim measurements together.
      • Record the measurement. This is the thickness for the left side shim pack
    4. Calculate the average of the 3 measurements for each shim.
      5. 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

    5. Assemble a new left side shim pack by decreasing the appropriate amount of thickness from the original left side shim pack.
      6. NOTE:

      Measure each shim separately.

    6. Measure the thickness of right side shim or the shim and service spacer in 3 locations.
      7. NOTE:
      • Add the average of each of the shim measurements together.
      • Record the measurement. This is the thickness for the right side shim pack.
    7. Calculate the average of the 3 measurements for each shim.
    8. Assemble a new right side shim pack by increasing 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 increase the backlash by 0.05 mm (0.002 in), add 0.10 mm (0.004 in) of thickness to the right side shim pack.
  12. Use the following procedure to decrease the backlash if the backlash is too large:
    1. Remove the bearing cap bolts and the bearing caps.
      2. NOTE:

      Mark the bearing cups and the shims left or right.

    2. Remove the differential case assembly with the bearing cups and the shims.
      3. NOTE:
      • Measure the production shim or the shim and service spacer in 3 locations.
      • Measure each shim separately.
    3. Measure the thickness of left side shim pack.
      4. NOTE:
      • Add the average of each of the shim measurements together.
      • Record the measurement. This is the thickness for the left side shim pack.
    4. Calculate the average of the 3 measurements for each shim.
    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. NOTE:
      • Measure the shim or the shim and service spacer in 3 locations.
      • Measure each shim separately.
    6. Measure the thickness of right side shim pack.
      7. NOTE:
      • Add the average of each of the shim measurements together.
      • Record the measurement. This is the thickness for the right side shim pack.
    7. Calculate the average of the 3 measurements for each shim.
    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.
  13. Install the differential case assembly with the bearing cups.
  14. Instal the left side service shims between the axle housing and the differential case.
  15. Instal the right side service shims between the axle housing and the differential case.
  16. GM3259565
    NOTE:

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

    Using the brass drift for 9.5/9.76 axle, install the left side service spacer

  17. Using the brass drift for 9.5/9.76 axle, install the right side service spacer
  18. Install the bearing caps and bolts and tighten to:
    1. First pass at 60 N.m (44 lb ft)
    2. Final pass an additional 30 degrees
  19. Recheck the backlash and adjust, if necessary.
  20. 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 .
    21. NOTE:

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

  21. Tighten the differential bearing cap bolts to:
    1. First pass at 60 N.m (44 lb ft)
    2. Final pass an additional 30 degrees
  22. Measure the drive pinion and differential case side bearing preload and adjust, if necessary following the steps above.
  23. 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 .
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