Brake Shoe: Adjustments

The rear drum brakes, have self-adjusting shoe mechanisms that assure correct lining-to-drum clearances at all times. The automatic adjusters operate only when the brakes are applied as the vehicle is moving rearward.

Although the brakes are self-adjusting, an initial adjustment is necessary after the brake shoes have been replaced, or when the length of the star wheel adjuster has been changed during some other service operation.


1. Raise and support vehicle, then remove rear wheels and brake drums.
2. Check to make sure that parking brake cable linkage and levers on secondary brake shoe are in ``free'' position.

Measuring Brake Drum Inside Diameter:

Adjusting Brake Shoe To Drum Clearance:

Brake Adjustment Using Tool J-21177
3. Using tool J-21177, measure brake drum inside diameter.
4. Turn brake adjusting screw to expand shoes to diameter obtained on outside caliper portion of tool J-21177.
5. Install drums.

CAUTION: Whenever rear drum brakes are serviced, the parking brake linkage cable at the equalizer must always be readjusted to prevent possible damage to brake shoes.

6. Adjust parking brake. Refer to Parking Brake Adjustment.
Adjustments
7. Install wheels and tires and lower vehicle to floor.
8. Drive vehicle alternately forward and backward, applying brakes moderately, to obtain satisfactory pedal height.

Adjusting Brakes:

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Brake Adjustment Determined By Drag
1. Remove adjusting hole knockout plate from brake drum and back off adjusting screw using screwdriver and adjusting tool.


NOTE: The knockout plate must be drilled out using a 11 mm (7/16 inch) drill. After adjustment, install rubber adjusting hole cover GM P/N 5464803 or equivalent into adjusting hole to prevent dirt or contamination from entering drum brake assembly.


2. Using suitable tool, turn brake adjusting screw to expand brake shoes at each wheel until wheel can just be turned by hand. Drag should be equal on all wheels.
3. Back off adjusting screw at each wheel 33 notches.

NOTE: Brakes should have no drag after the screw has been backed off about 15 notches. If a heavy drag is present check the parking brake cable for free operation. The brake lever must return to the released position without sticking or binding.
4. Install adjusting hole cover in brake backing plate.

CAUTION: Whenever rear drum brakes are serviced, the parking brake linkage cable at the equalizer must always be readjusted to prevent possible damage to brake shoes.

5. Adjust parking brake. Refer to Parking Brake Adjustment.Adjustments
6. Install wheels and tires and lower vehicle to floor.
7. Drive vehicle alternately forward and backward, applying brakes moderately, to obtain satisfactory pedal height.