Chevrolet Blazer/Jimmy 1969-1982 Repair Guide

Brake Drums

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REMOVAL & INSTALLATION



Drums on all models can be removed by raising the vehicle, removing the wheel lugs and the tire, and pulling the drum from the brake assembly. If the brake drums have been scored deeply, the brake adjuster must be backed off so that the brake shoes will retract from the drum. Some drums are retained by two screws to the hub, and can be removed after removing the screws.

The adjuster can be backed off by inserting a brake adjusting tool or screwdriver through the access hole provided. Hold the adjuster lever away from the starwheel; turn the starwheel. In some cases the access hole is in the brake drum. A metal cover plate is over the hole. This may be removed by using a hammer and chisel.

Make sure all metal particles are removed from the brake drum before reassembly.

To install, reverse the removal procedure.


CAUTION
Do not blow the brake dust out of the drums with compressed air. Powdered asbestos has been found to be a cancer-producing agent.

INSPECTION





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Fig. Fig. 1 To remove the drum brake assembly, raise the rear of the vehicle and support it with jackstands



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Fig. Fig. 2 1. Brake drum 2. Brake adjusting tool 3. Access hole If necessary, back off the adjuster using an adjusting tool inserted through the access hole



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Fig. Fig. 3 Remove the brake drum from the vehicle

Lining

Remove the drum and inspect the lining thickness on both brake shoes. A front brake lining should be replaced if it is less than 1 / 8 inch thick at the lowest point on the brake shoe. The wear limit for rear brake linings is 1 / 16 inch.

Brake shoes should always be replaced in axle sets. The wear specifications given may disagree with your state inspection rules.

Drum

When a drum is removed, it should be inspected for cracks, scores, or other imperfections. These must be corrected before the drum is replaced.


WARNING
If the drum is found to be cracked, replace it. Do not attempt to service a cracked drum.

Minor drum score marks can be removed with fine emery cloth. Heavy score marks must be removed by "turning the drum." This is removing metal from the entire inner surface of the drum on a lathe in order to level the surface. Automotive machine shops and some large parts stores are equipped to perform this operation.

If the drum is not scored, it should be polished with fine emery cloth before replacement. If the drum is resurfaced, it should not be enlarged more than 0.060 inch.

Your state inspection law may disagree with this specification.

It is advisable, while the drums are off, to check them for out-of-round. An inside micrometer is necessary for an exact measurement; therefore unless this tool is available, the drums should be taken to a machine shop to be checked. Any drum which is more than 0.006 inch out-of-round will result in an inaccurate brake adjustment and other problems, and should be refinished or replaced.

Make all measurements at right angles to each other and at the open and closed edges of the drum machined surface.

 
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