REAR DRUM BRAKES
See Figures 1, 2, 3 and 4
Normal adjustments of the rear drum brakes are automatic and are made during the reverse applications of the brakes. ONLY, if the lining has been renewed or if the self adjusters haven't worked properly, should the following procedure be performed.
The following procedure requires the use of the GM Brake Adjustment tool No. J-4735 or equivalent.
- Raise and support the rear of the vehicle on jackstands.
- Using a punch and a hammer, at the rear of the backing plate, knock out the lanced metal area near the star wheel assembly.
When 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.
Backing 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.
BRAKE PEDAL TRAVEL
See Figure 5
The brake pedal travel is the distance the pedal moves toward the floor from the fully released position. Inspection should be made with 90 lbs. pressure on the brake pedal, when the brake system is cold. The brake pedal travel should be 4 1 / 2 in. (114mm) for manual, or 3 1 / 2 in. (89mm) for power.
If equipped with power brakes, be sure to pump the brake pedal at least 3 times with the engine OFF, before making the brake pedal check.
- From under the dash, remove the pushrod-to-pedal clevis pin and separate the pushrod from the brake pedal.
- Loosen the pushrod adjuster lock nut, then adjust the pushrod.
- After the correct travel is established, reverse the removal procedure.