Pinion Depth Adjustment

Tools Required 

• J 34925  Pinion Setting Gage and Components
• J 45230  Pinion Setting Gage Block
• 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 J 21777-35 (1), the J 21777-43  (2), the J 21777-42 (3),  and the J 45230,  8.0 inch axle, or the J 21777-29, 8.6 inch axle (4) into the axle housing as shown.
4. While holding the J 21777-43  stationary, install an inch-pound torque wrench on the nut of the J 21777-43. 

   Tighten 

   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.

5. Rotate the assembly several times in both directions in order to seat the pinion bearings.
6. Check the rotating torque of the assembly. If the torque is less than 1.7 N.m (15 lb in), continue to 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.
   Fig 1: Assembling J 21777-35 (1), J 21777-43 (2), J 21777-42 (3), J 45230, Or J 21777-29,

   Courtesy of GENERAL MOTORS CORP.
7. as shown.
8. Rotate the J 21777-1 within the J 21777-45.  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.
   Fig 2: Assembling J 21777-45 (1,2) To J 21777-1 (3)

   Courtesy of GENERAL MOTORS CORP.
9. Align the plunger of the J 21777-1 (1) to the J 45230,  8.0 inch axle, or the J 21777-29, 8.6 inch axle (2).
10. 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 J8001  and push down on the J8001  until the needle the J 8001  has turned 3/4 of a turn clockwise.
    4. Tighten the clamp on the J8001  finger tight.
11. Move the plunger of the J 21777-1 back and forth until the needle of the J8001  indicates the greatest deflection.
    Fig 3: Aligning Plunger Of J 21777-1 (1)

    Courtesy of GENERAL MOTORS CORP.

    The deflection is the point where the needle changes direction.

12. At the greatest point of deflection, move the housing of the J 8001  until the needle indicates ZERO.
13. 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.
14. Rotate the plunger of the J 21777-1 away from the J 45230,  8.0 inch axle, or the J 21777-29, 8.6 inch axle, until it no longer touches the J 45230  or the J 21777-29.
15. The value indicated on the J 8001  is the thickness of the shim needed in order to set the depth of the pinion.
16. Select the shim that indicates the proper thickness. Measure the shim with a micrometer in order to verify that the thickness is correct.
17. Remove the pinion depth setting tools.
18. Remove the pinion bearings.
    Fig 4: Measuring Shim Thickness With Micrometer

    Courtesy of GENERAL MOTORS CORP.
19. Install the pinion shim between the pinion gear and the inner pinion bearing. Refer to DRIVE PINION BEARINGS REPLACEMENT   .