Normal adjustments of the rear drum brakes are automatic and are made when the brakes are applied while the vehicle is driving in reverse. ONLY, if the linings have been replaced or if the self adjusters haven't worked properly, should the following procedure be performed.
- Raise and safely support the vehicle.
Using a punch and a hammer, at the rear of the backing plate, knock out the lanced metal area near the star wheel assembly.
NOTEWhen knocking out the lanced metal area from the backing plate, the wheels must be removed and all of the metal pieces discarded.
Using the GM Brake Adjustment tool No. J-4735 or equivalent, insert it into the slot and engage the lowest possible tooth on the star wheel. Move the end of the brake tool downward to move the star wheel upward and expand the adjusting screw. Repeat this operation until the brakes lock the wheel.
- Insert a small screwdriver or piece of firm wire (coat hanger wire) into the adjusting slot and push the automatic adjuster lever out and free of the star wheel on the adjusting screw.
- While holding the adjusting lever out of the way, engage the topmost tooth possible on the star wheel (with the brake tool). Move the end of the adjusting tool upward to move the adjusting screw star wheel downward and contact the adjusting screw. Back off the adjusting screw star wheel until the wheel spins freely with a minimum of drag. Keep track of the number of turns the star wheel is backed off.
Repeat this operation for the other side. When backing off the brakes on the other side, the adjusting lever must be backed off the same number of turns to prevent side-to-side brake pull.
NOTEBacking off the star wheel 12 notches (clicks) is usually enough to eliminate brake drag.
- Repeat this operation on the other side of the rear brake system.
- After the brakes are adjusted, install a rubber hole cover into the backing plate slot. To complete the brake adjustment operation, make several stops while backing the vehicle to equalize the wheels.
- Road test the vehicle.
Removal & Installation
- Before servicing the vehicle, refer to the Precautions Section.
- Remove wheel and tire assembly.
- Remove brake drum.
- Remove return springs from the brake shoes.
- Remove shoe guide.
- Remove hold-down springs and pins.
- Remove actuator lever and pivot.
- Remove lever return spring.
- Remove actuator link.
- Remove parking brake strut and spring.
- Remove parking brake lever.
- Remove brake shoes and the adjuster assembly.
- Lubricate the contact points on the backing plate and the adjuster with lithium grease.
- Install parking brake lever, adjusting screw and spring assembly.
- Install shoe assembly onto the backing plate.
- Install parking brake lever, strut and strut spring.
- Install actuator lever and lever pivot.
- Install actuator link.
- Install lever spring, the hold-down pins and springs.
- Install shoe guide.
- Install return springs and install the brake drum in position.
Adjust the brakes as follows:
- Remove the knockout area in the backing plate, behind the adjuster assembly.
- Ensure the parking brake system is adjusted properly with no tension on the cables or parking brake lever. The tops of the shoes should be firmly seated against the upper spring retaining anchor, if not as specified, loosen the parking brake cables.
- Install the drum and turn the brake adjuster until the wheels can just be turned by hand.
- Then, back the adjuster off 24 notches. No brake drag should be felt after 12 notches.
- Install an adjusting hole plug in the backing plate to prevent dirt and moisture from entering.
- Readjust the parking brake cable as necessary.
- Install the wheel and tire assemblies.
Refill the master cylinder and pump pedal to attain full brake pedal before Road-testing the vehicle.