GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 Safari - 4WD 🢒 Steering 🢒 Power Steering System 🢒 Rack Piston and Worm Shaft Replacement - Off Vehicle

Disassembly Procedure

Tools Required

J 21552 Rack Piston Arbor


    Object Number: 322017 Size: SH
  1. Remove the pitman shaft and side cover. Refer to Steering Gear Pitman Shaft and Housing Cover Replacement - Off Vehicle .
  2. Remove the housing end plug (1). Refer to Steering Gear Housing Plug Replacement - Off Vehicle .
  3. Turn the stub shaft counterclockwise until the rack piston (2) begins to come out of the steering gear housing.
  4. Remove the rack piston plug (1).
  5. Insert the J 21552 into the bore of the rack piston (2).
  6. Hold the J 21552 tightly against the worn shaft while turning the stub shaft counterclockwise.

    7. The rack piston will be forced onto the J 21552 and will hold the rack piston balls in place.


    Object Number: 322087 Size: SH
  7. Remove the following items as an assembly from the steering gear housing (9):
    8. • The rack piston (4)
    • The rack piston balls (5)
    • The J 21552
  8. Remove the valve. Refer to Steering Gear Valve Replacement - Off Vehicle .
  9. Remove the worm shaft (14).
  10. Remove the thrust bearing (12) and the flat races (11, 13).
  11. Remove the flat races (11).
  12. Remove the J 21552 from the rack piston (4).
  13. Remove the rack piston balls (5).
  14. Remove the following items from the rack piston (4):
    15. 14.1. The screws (8)
    14.2. The clamp (7)
    14.3. The ball guide (6)
  15. Remove the teflon ring (2).
  16. Remove the O-ring seal (3).
  17. Clean all of the disassembled parts.
  18. Inspect all of the disassembled parts for wear.
  19. Replace the parts if necessary.

Assembly Procedure

Tools Required

    • J 8947 Rack Piston Ring Compressor
    • J 21552 Rack Piston Arbor
  1. Lubricate the O-ring seal and the teflon ring with power steering fluid.

    2. Object Number: 322018 Size: SH
  2. Install the O-ring seal (3) and the teflon ring (2).
  3. Install the worm shaft (14) to the rack piston (4) outside of the steering gear housing (9).

    4. Fully seat the worm shaft to the rack piston.


    Object Number: 322019 Size: SH
  4. Align the worm shaft spiral groove with the rack piston ball return guide hole (1).
  5. Lubricate the rack piston balls with power steering fluid.

    6. Caution: In order to avoid injury and/or component damage, install all of the rack piston balls into the rack piston. Install the rack piston balls in the correct order. If you do not correctly install all of the rack piston balls, the steering gear may not operate or may wear out quickly.

    Important: The black rack piston balls are smaller than the silver rack piston balls. Install the black and the silver rack piston balls alternately into the rack piston and the ball guide to maintain the rack piston to the worm shaft preload.

  6. Insert the rack piston balls through the ball return guide hole (1) while turning worm shaft (2) counterclockwise in order to install the rack piston balls into the rack piston.

    7. Object Number: 322022 Size: SH
  7. Install the remaining rack piston balls (3) into the ball guide (1) using grease at each end (2) to retain the rack piston balls (3).

    8. Object Number: 322024 Size: SH
  8. Install the ball guide (5) to the rack piston (4).
  9. Install the ball guide clamp (6).

    10. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  10. Install the screws (7).

    11. Tighten
    Tighten the screws (7) to 4.9 N·m (58 lb in).

  11. Insert J 21552 into the bore of the rack piston while turning the worm shaft counterclockwise. The turning of the worm shaft forces the rack piston onto J 21552 . The rack piston balls remain in place.

    12. Object Number: 322025 Size: SH
  12. Install the flat races (2, 4) and the thrust bearing (3) onto the worm shaft (1).

    13. Object Number: 322026 Size: SH
  13. Install the worm shaft (4) to the steering gear housing (3).
  14. Install the valve. Refer to Steering Gear Valve Replacement - Off Vehicle .
  15. Install the rack piston (2) to the worm shaft (4) from the J 21552 using the J 8947 to compress the seals.

    16. Caution: In order to avoid injury and/or component damage, install all of the rack piston balls into the rack piston. Install the rack piston balls in the correct order. If you do not correctly install all of the rack piston balls, the steering gear may not operate or may wear out quickly.

  16. Hold the J 21552 tightly against the worm shaft (4).
  17. Turn the stub shaft clockwise until the rack piston (2) is seated on the worm shaft (4).
  18. Install the rack piston plug.

    19. Tighten
    Tighten the rack piston plug to 150 N·m (111 lb ft).

  19. Install the housing end plug (1). Refer to Steering Gear Housing Plug Replacement - Off Vehicle .
  20. Install the pitman shaft and side cover. Refer to Steering Gear Pitman Shaft and Housing Cover Replacement - Off Vehicle .
  21. Adjust the worm thrust bearing preload. Refer to Steering Gear Worm Gear Thrust Bearing Preload Adjustment - Off Vehicle .
  22. Adjust the pitman shaft over center preload. Refer to Steering Gear Pitman Shaft Over-Center Preload Adjustment - Off Vehicle .