GM Service Manual Online
For 1990-2009 cars only

Tools Required

J 21177-A Drum to Brake Shoe Clearance Gage

  1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle .
  2. Remove the rear tire and wheel assemblies. Refer to Tire and Wheel Removal and Installation .
  3. Caution: Refer to Brake Dust Caution in the Preface section.


    Object Number: 492729  Size: SH
  4. Ensure that the park brake lever is in the fully released position.
  5. Pull down on the front cable (3) and disconnect the short cable (2) leading to the drum backing plate from the cable connector (1). Do this step for both sides of the vehicle in order to ensure no cable drag is present.


    Object Number: 1179727  Size: SH
  6. Remove the rear brake drums. Refer to Brake Drum Replacement .

  7. Object Number: 891757  Size: SH
  8. Position the J 21177-A to widest point of the brake drum inside diameter.
  9. Firmly hand tighten the set screw on the J 21177-A .

  10. Object Number: 891758  Size: SH
  11. Remove the J 21177-A from the brake drum and position it over the corresponding brake shoe assembly at its widest point.
  12. While holding the J 21177-A in position, insert a 0.635 mm (0.025 in) feeler gage between one side of the J 21177-A , and the corresponding brake shoe.
  13. Rotate the brake shoe adjuster screw until the brake shoes contact the J 21177-A , and the feeler gage.
  14. Specification
    Brake shoe-to-drum clearance: 0.635 mm (0.025 in)

  15. Repeat the above steps for the opposite brake drum and brake shoe assembly.

  16. Object Number: 1179727  Size: SH
  17. Install the brake drums. Refer to Brake Drum Replacement .

  18. Object Number: 492729  Size: SH
  19. Pull down on the front cable (3) and connect the short cable (2) leading to the drum backing plate to the cable connector (1). Repeat for opposite side.
  20. Adjust the park brake. Refer to Park Brake Adjustment .
  21. Install the rear tire and wheel assemblies. Refer to Tire and Wheel Removal and Installation .
  22. Lower the vehicle.