Pinion Depth Adjustment (8.6 Inch, 9.5 Inch, 11.5 Inch Axles)

Tools Required

• J 45108  Pinion Setting Gage Block, 9.5 inch Axle. See Special Tools and Equipment .
• J 21777-86  Side Bearing Disc, 9.5 inch Axle, 2 Required. See Special Tools and Equipment .
• J 34925 Pinion Setting Gauge Kit
• J 44416  Pinion Setting Adapter Kit, 11.5 inch axle. See Special Tools and Equipment .
• J 8001  Dial Indicator Set

IMPORTANT: Make sure all of the tools, the differential side bearing bores, and the pinion bearing cups are clean before proceeding.
1. Lubricate the pinion bearings with axle lubricant. Refer to Fluid and Lubricant Recommendations in Maintenance and Lubrication.
2. Install the pinion bearings into the axle housing.
3. Assemble the following components into the axle housing:
   • For the 8.6 in axle, assemble the J 21777-35 (1), the J 21777-43 (2), the J 21777-42 (3), and the J 21777-29 (4) as shown.
   • For the 9.5 in axle, assemble the J 21777-8 (1), the J 21777-43 (2), the J 21777-42 (3), and the J 45108  (4) as shown.
   • For the 11.5 in axle, assemble the J 44416-3 (1,4), the J 21777-43 (2), and the J 44416-2 (3) as shown.
Fig 1: Assembling Special Tools In Axle Housing
Courtesy of GENERAL MOTORS CORP.
4. While holding the J 21777-43 stationary, install an inch-pound torque wrench on the nut of the J 21777-43 and tighten the nut until a rotating torque of 1.7 N.m (15 lb in) is obtained.

   Rotate the assembly several times in both directions in order to seat the pinion bearings.

5. Check the rotating torque of the assembly. If the torque is less than 1.7 N.m (15 lb in), tighten the nut on the J 21777-43 until a rotating torque of 1.7-2.3 N.m (15-20 lb in) is obtained.
6. Assemble the following components into the differential carrier bore of the axle housing:
   • For the 8.6 in axle, assemble the J 21777-45 (1, 2) to the J 21777-1 (3) as shown.
   • For the 9.5 in axle, assemble the J 21777-86 (1, 2) to the J 21777-1 (3) as shown.
   • For the 11.5 in axle, assemble the J 44416-1 (1, 2) to the J 21777-1 (3) as shown.
Fig 2: Assembling Special Tools In Differential Carrier Bore
Courtesy of GENERAL MOTORS CORP.
7. Install the bearing caps.
NOTE: Refer to Fastener Notice in Cautions and Notices.
8. Install the bearing cap bolts.

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

9. Rotate the J 21777-1 within the J 21777-45, 8.6 in axle, or the J 21777-86, 9.5 in axle, or the J 44416-1, 11.5 in axle. The J 21777-1 must rotate back and forth freely within the discs. If the J 21777-1 does not rotate freely, disassemble the components, inspect for proper seating and/or mis-aligned components and re-assemble.
10. Align the plunger of the J 21777-1 (1) to the 8.5 in gauge block setting of the J 21777-29, 8.6 in axle, or the J 45108  , 9.5 in axle, or the J 44416-3, 11.5 in axle (2).
Fig 3: J 21777-1 & J 44416-3
Courtesy of GENERAL MOTORS CORP.
11. Install the J 8001  to the J 21777-1 as follows:
    1. Loosely clamp the J 8001  onto the stem on the J 21777-1.
    2. Place the contact pad of the J 8001  onto the mounting post of the J 21777-1.
    3. With the contact pad of the J 8001  touching the mounting post of the J 21777-1, loosen the lock nut on the J 8001  and push down on the J 8001  until the needle the J 8001  has turned 3/4 of a turn clockwise.
    4. Tighten the clamp on the J 8001  finger tight.
12. Move the plunger of the J 21777-1 back and forth until the needle of the J 8001  indicates the greatest deflection.

    The deflection is the point where the needle changes direction.

13. At the greatest point of deflection, move the housing of the J 8001  until the needle indicates zero.
Fig 4: Moving The Housing J 8001
Courtesy of GENERAL MOTORS CORP.
14. Move the plunger of the J 21777-1 back and forth again to verify the zero setting. Adjust the housing of the J 8001  as necessary to set the needle to zero.
15. Rotate the plunger of the J 21777-1 away from the J 21777-29, 8.6 in axle, the J 45108  , 9.5 in axle, or the J 44416-3, 11.5 in axle, until it no longer touches the J 21777-29, the J 45108  , or the J 44416-3.
16. The value indicated on the J 8001  is the thickness of the shim needed in order to set the depth of the pinion.
17. Select the shim that indicates the proper thickness. Measure the shim with a micrometer in order to verify that the thickness is correct.
18. Remove the pinion depth setting tools.
19. Remove the pinion bearings.
20. Install the pinion shim between the pinion gear and the inner pinion bearing. Refer to Drive Pinion Bearings Replacement (8.6, 9.5, 11.5 Inch Axles)  or Drive Pinion Bearings Replacement (9.75 Inch Axle)  or Drive Pinion Bearings Replacement (10.5 Inch Axle) .