GM Service Manual Online
For 1990-2009 cars only

Special Tools

J 21177-A Drum to Brake Shoe Clearance Gage

Warning: Refer to Brake Dust Warning in the Preface section.

Note: The rear brakes must be adjusted manually after replacing the rear brake shoes.


    Object Number: 1254558  Size: SH
  1. Raise the vehicle. Refer to Lifting and Jacking the Vehicle.
  2. Loosen the adjuster nut for the park brakes.
  3. Remove the brake drum. Refer to Brake Drum Replacement.

  4. Object Number: 1241711  Size: SH
  5. Using the J 21177-A  (1), measure the inside diameter of the brake drum.

  6. Object Number: 1241702  Size: SH

    Note: When performing the following service procedure, ensure that the J 21177-A  (1) is level, before taking the measurement.

  7. Using the J 21177-A  (1), adjust the brakes shoes until there is approximately 0.76 mm (.030 in) clearance between the rear brake shoes and the rear brake drum.

  8. Object Number: 1254558  Size: SH
  9. Install the brake drum.
  10. With heavy force, apply the brake pedal 2 times in order to center and adjust the brake shoes.
  11. Inspect the drums again for light drag. If necessary, repeat the previous step for adjusting the brakes.
  12. Lower the vehicle. Refer to Lifting and Jacking the Vehicle.
  13. Adjust the park brake. Refer to Park Brake Adjustment.