Pinion Depth Adjustment

Tools Required 

• J 8001  Dial Indicator Set
• J 21777-40  Rear Pilot Washer
• J 21777-42  Front Pilot Washer
• J 21777-43  Stud Assembly Bolt
• J 21777-45  Side Bearing Discs
• J 21777-1  Arbor
• J 21777-29  Gage Plate
• J 21777-35  Rear Pilot Washer
• J 23597-1  Arbor
• J 23597-11  Gage Plate

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.
2. Install the pinion bearings into the axle housing.
3. Assemble the following components into the axle housing:
   • For the 7.6 inch axle, assemble the J 21777-40  (1), the J 21777-43  (2), the J 21777-42  (3), and the J 21777-45  (4) as shown.
   • For the 8.6 inch 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.
   Fig 1: Assembling Different Components Into 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 2.2 N.m (20 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 1.7-2.8 N.m (15-25 lb in) is obtained.
6. Assemble the following components into the differential carrier bore of the axle housing:
   • For the 7.6 inch axle, assemble the J 21777-45  (1, 2) to the J 23597-1  (3) as shown.
   • For the 8.6 inch axle, assemble the J 21777-45  (1,2) to the J 21777-1 (3) as shown.
   Fig 2: Assembling J 21777-45 to J 23597-1

   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 23597-1  (7.6 inch axle) or the J 21777-1 (8.6 inch axle) within the J 21777-45  . The J 23597-1  or the J 21777-1 must rotate back and forth freely within the discs. If the J 23597-1  or the J 21777-1 does not rotate freely, disassemble the components, inspect for proper seating and/or mis-aligned components and reassemble.
10. Align the plunger of the J 23597-1  (1) to the J 23597-11  (2) (7.6 inch axle) or the J 21777-1 (1) to the J 21777-29 (2) (8.6 inch axle).
    Fig 3: Aligning Plunger

    Courtesy of GENERAL MOTORS CORP.
11. Install the J 8001  to the J 23597-1  or the J 21777-1 as follows:
    1. 11.1. Loosely clamp the J 8001  onto the stem on the J 23597-1  or the J 21777-1.
    2. 11.2. Place the contact pad of the J 8001  onto the mounting post of the J 23597-1  or the J 21777-1.
    3. 11.3. With the contact pad of the J 8001  touching the mounting post of the J 23597-1  or 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. 11.4. Tighten the clamp on the J 8001  finger tight.
12. Move the plunger of the J 23597-1  or 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.
14. Move the plunger of the J 23597-1  or 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 23597-1  from the J 23597-11  (7.6 inch axle) or the J 21777-1 away from the J 21777-29 (8.6 inch axle) until it no longer touches the J 23597-11  (7.6 inch axle) or the J 21777-29 (8.6 inch axle).
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  .
    Fig 4: Checking Proper Thickness

    Courtesy of GENERAL MOTORS CORP.