Drum Brake Adjustment

Tools Required 

J 21177-A  Drum-to-Brake Shoe Clearance Gauge

1. Raise and support the vehicle. Refer to LIFTING AND JACKING THE VEHICLE .
2. Remove the tire and wheel assembly from the vehicle. Refer to TIRE AND WHEEL REMOVAL AND INSTALLATION .
3. Insert a screwdriver through the hole in the backing plate. Hold the automatic adjusting lever away from the adjusting bolt.
4. Reduce the brake shoe adjustment by turning the adjusting bolt. Use another screwdriver.
5. Remove the drum.
6. Insert J 21177-A. Ensure that the gauge contacts the inner diameter of the brake drum.
   Fig 1: Inserting J 21177-A

   Courtesy of GENERAL MOTORS CORP.
7. Position J 21177-A over the shoes and linings.
8. Turn the adjuster until the primary and secondary shoes and linings contact J 21177-A.

   The outside diameter of the shoes and linings should be approximately 0.6 mm (0.024 in) less than the diameter of the brake drum.

9. Install the drum. Refer to Brake Drum Replacement .
10. Install the tire and wheel assembly to the vehicle. Refer to TIRE AND WHEEL REMOVAL AND INSTALLATION .
11. Lower the vehicle.