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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 900 (Rear Drive Axle) >> Repair Instructions >> Backlash Adjustment (10.5, 11.5 Inch Axles)

Backlash Adjustment (10.5, 11.5 Inch Axles)

WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Tools Required

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.
    Fig 1: Measuring Pinion Rotating Torque
    GM661077Courtesy 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 3.4-6.2 N.m (30-55 lb in) for new bearings or 2.8-5.1 N.m ( 25-45 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 (10.5 Inch, 11.5 Inch Axle)  or Differential Replacement (8.6, 9.5/9.5LD Inch Axles)  and Drive Pinion Bearings Replacement (8.6, 9.5/9.5LD, and 11.5 Inch Axles) .
    5. Fig 2: Measuring Ring Gear Backlash
    GM6946Courtesy of GENERAL MOTORS CORP.
  5. Install the J 25025-1  and the J 8001  to the axle housing as shown. See Special Tools .
  6. Place the indicator stem of the J 8001-3  at the heel end of a gear tooth. See Special Tools .
  7. Set the J 8001-3  so that the stem is aligned with the gear rotation and perpendicular to the tooth angle. See Special Tools .
  8. Preload the dial of the J 8001-3  . See Special Tools .

    Align the needle and the dial face of the J 8001-3  to ZERO. See Special Tools .

  9. While holding the drive pinion stationary, move the ring gear back and forth.

    Measure and record the backlash.

  10. Repeat the measuring procedure at eight points around the ring gear.

    Specification:  The difference between the backlash at all of the measuring points should not vary by more than 0.05 mm (0.002 in).

  11. If the difference between the backlash at all of the measuring points varies by more than 0.05 mm (0.002 in), inspect for the following conditions:
    • Burrs
    • A distorted case flange
    • Uneven bolting
  12. If the difference between all the measuring points is within specifications, the backlash at the minimum lash point measured should be:

    Specification:  The backlash between the ring gear and the drive pinion should be between 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).

    13. Fig 3: Turning Adjusters Using J 24429
    GM694535Courtesy of GENERAL MOTORS CORP.
  13. If the backlash is not within specifications, adjust the backlash by performing the following steps:
    1. Remove the differential bearing adjuster nut retainers bolts.
    2. Remove the differential bearing adjuster nut retainers.
    3. Remove the bearing cap bolts.
    4. Remove the bearing caps. Mark the bearing caps left and right.
    5. If the backlash is too small, increase the backlash by turning the left differential bearing adjuster in one slot and the right differential bearing adjuster out one slot using the J 24429  until the correct backlash is obtained. See Special Tools .
    6. If the backlash is too large, decrease the backlash by turning the right differential bearing adjuster in one slot and the left differential bearing adjuster out one slot using the J 24429  until the correct backlash is obtained. See Special Tools .
  14. Install the bearing caps.
    15. NOTE: Refer to Fastener Notice .
  15. Install the bearing cap bolts.

    Tighten: 

    • Tighten the bearing cap bolts to 185 N.m (136 lb ft) (10.5 inch axle).
    • Tighten the bearing cap bolts to 207 N.m (153 lb ft) (11.5 inch axle).

  16. Recheck the backlash following the steps above to verify that the backlash is within specifications.
  17. Install the differential bearing adjuster nut retainers.
  18. Install the differential bearing adjuster nut retainer bolts.

    Tighten:  Tighten the differential bearing adjuster nut retainer nut bolts to 27 N.m (20 lb ft).

  19. Measure the drive pinion and differential case side bearing preload and adjust, if necessary following the steps above.
  20. 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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