GM Full-Size Trucks 1988-1998 Repair Information

Brake Drums



Semi-Floating Axles

Older brake pads or shoes may contain asbestos, which has been determined to be a cancer causing agent. Never clean the brake surfaces with compressed air! Avoid inhaling any dust from any brake surface! When cleaning brake surfaces, use a commercially available brake cleaning fluid.

See Figure 1

  1. Raise and support the rear end on jackstands.
  3. Remove the wheel.
  5. Pull the drum from the brake assembly. If the brake drums have been scored from worn linings, the brake adjuster must be backed off so that the brake shoes will retract from the drum. The adjuster can be backed off by inserting a brake adjusting tool through the access hole provided. In some cases the access hole is provided in the brake drum. A metal cover plate is over the hole. This may be removed by using a hammer and chisel.

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Fig. Fig. 1: You may have to back off the automatic adjuster before you can pull the drum from the brake assembly

  1. To install, reverse the removal procedure.

Full Floating Axles

To remove the drums from full floating rear axles, use the Axle Shaft Removal & Installation procedure . Full floating rear axles can readily be identified by the bearing housing protruding through the center of the wheel.

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


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

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 has to be resurfaced, it should not be enlarged more than the maximum wear limit. Refer to the brake specifications chart in this section for the brake drum original inside diameter and maximum wear limit specifications for your vehicle.

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 in. (0.1524mm) 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.