GM Full-Size Trucks 1980-1987 Repair Guide



All models have front disc brakes. This single piston caliper is a sliding type. No brake adjustment is necessary once the brake pads have been seated against the rotor. All 1980-87 trucks over 9000 GVWR use a Bendix disc brake assembly.

The single piston system is a closed system with fluid pressure being exerted on two surfaces: on the piston itself and in the opposite direction against the bottom of the bore of the caliper housing. There is equal pressure since the area of the piston and the bottom of the caliper bore are equal.

When hydraulic pressure is applied to the piston, it is transmitted to the inner brake pad lining which contacts the inner surface of the disc. This pulls the caliper assembly inboard as it slides on the four rubber bushings. As the caliper slides, the outer lining applies force to the outer surface of the disc and in this manner the two surfaces brake the vehicle.

Since the hydraulic pressure is equally applied to both brake pads there will be no flexing or distortion of the pad and if the unit is operating correctly, the pad wear should be equal.

This type of disc brake uses a very small running clearance between pad and rotor. As the brake linings wear, the caliper assembly moves inward and the brake fluid from the reservoir fills the area behind the piston so that brake pedal travel is not increased. Therefore, you will still have a high pedal even though the pad could be worn to the metal backing.

Because the brake pads are in close contact with the rotor, this gives the advantage of increased brake response, reduced brake pedal travel, and faster generation of hydraulic line pressure. The pad being close to the rotor disc also cleans it of foreign material.

The system is composed of the hub and disc assembly, the shield, the support, the caliper assembly, and the linings. The disc is vented with cooling fins which dissipate heat.

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