GM Full-Size Trucks 1980-1987 Repair Guide

Brake Pads

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INSPECTION



See Figure 1

To measure the lining thickness at a rivet head, removal of the caliper and pad is required.

Support the front suspension or axle on jackstands and remove the wheels. Look in at the ends of the caliper to check the lining thickness of the outer pad. Look through the inspection hole in the top of the caliper to check the thickness of the inner pad. Minimum acceptable pad thickness is 1 /32 in. from the rivet heads on original equipment riveted linings and 1 /32 in. lining thickness on bonded linings.

These manufacturer's specifications may not agree with your state inspection law.

All original equipment pads are the riveted type; unless you want to remove the pads to measure the actual thickness from the rivet heads, you will have to make the limit for visual inspection 1 /16 in. or more. The same applies if you don't know what kind of lining you have. All later original equipment pads and GM replacement pads have an integral wear sensor. This is a spring steel tab on the rear edge of the inner pad which produces a squeal by rubbing against the rotor to warn that the pads have reached their wear limit. They do not squeal when the brakes are applied.


WARNING
The squeal will eventually stop if the worn pads aren't replaced. Should this happen, replace the pads immediately to prevent expensive rotor (disc) damage.



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Fig. Fig. 1: New and worn brake pads

REMOVAL & INSTALLATION



See Figures 2, 3, 4 and 5

Remove one set of pads at a time so you have a reference for reassembly.



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Fig. Fig. 2: Use a C-clamp to retract the piston before removing the caliper assembly from the vehicle



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Fig. Fig. 3: Piston boot seating



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Fig. Fig. 4: With the fasteners removed, the caliper may be lifted from the rotor



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Fig. Fig. 5: If the caliper is not being removed, support it from the suspension using a length of wire

Delco Type

See Figures 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15

  1. Remove the cover on the master cylinder and siphon enough fluid out of the reservoirs to bring the level to 1 /3 full. This Step prevents spilling fluid when the piston is pushed back. Discard the fluid.
  2.  



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Fig. Fig. 6: Cross-section of a front disc brake caliper



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Fig. Fig. 7: Use a ratchet and hex key socket to loosen the Allen head bolts



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Fig. Fig. 8: Remove the Allen head slider bolts that retain the caliper

  1. Raise and support the vehicle. Remove the front wheels and tires.
  2.  
  3. Push the brake piston back into its bore using a C-clamp.
  4.  
  5. Remove the two Allen head bolts which hold the caliper and then lift the caliper off the disc.
  6.  


WARNING
Do not let the caliper assembly hang by the brake hose. Tie it out of the way with wire.



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Fig. Fig. 9: Pull the caliper from the rotor and remove the brake shoes



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Fig. Fig. 10: Carefully pry the spring retainers from the old brake shoes

  1. Remove the inboard and outboard pads. The shoe support spring will come off with the inner pad.
  2.  
  3. Install rubber bushings on all four caliper ears.
  4.  

It is essential that new sleeves and rubber bushings be used to ensure the proper function of the sliding caliper design. There is a special Tool recommended No. J-22835 for installing the sleeves.

  1. Position the sleeves so that the end toward the shoe and lining assemblies is flush with the machined surface of the ear.
  2.  



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Fig. Fig. 11: Apply anti-squeal compound to the back of the brake pads to prevent squeaking



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Fig. Fig. 12: Install the shoes to the caliper assembly making sure the retaining springs are properly seated

  1. Install the shoe support spring by replacing the single tang end of the spring over the notch in the center of the edge of the shoe. Then press the two tangs at the spring end of the inboard shoe spring over the bottom edge of the shoe so that they engage in the shoe securely.
  2.  
  3. Position the inboard shoe and lining assembly (with the spring attached) in the caliper so that the ear end of the shoe and lining is down and the bottom end up at an angle with the spring resting on the piston I.D.. Press down on both ends of the shoe until the shoe is in a flat position, resting on the piston. The spring end of the inboard shoe support spring should be resting on the I.D. of the piston.
  4.  

The wear sensor of the inboard shoe will be toward the rear of the caliper.

  1. Position the outboard shoe in the caliper with the ears at the top of the shoe over the caliper ears and the tab at the bottom of the shoe engaged in the caliper cutout. Be sure to note the right and left brake shoes.
  2.  



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Fig. Fig. 13: Inner brake pad installation in caliper



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Fig. Fig. 14: Caliper lubrication points at installation



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Fig. Fig. 15: Disc caliper installation

  1. Position the caliper over the rotor, lining up the holes in the caliper ears with the holes in the mounting bracket.
  2.  
  3. Install the bolts starting through the inboard caliper sleeves and ears and through the mounting bracket, making sure the ends of the bolts pass under the retaining ears on the inboard shoe. Push the bolts on through to engage the holes in the outboard shoes and the outboard caliper ears at the same time, threading the bolts into the mounting bracket. Torque the bolts to 35 ft. lbs.
  4.  
  5. Add fresh brake fluid as necessary to the master cylinder.
  6.  
  7. Pump the brake pedal to seat the linings against the rotor.
  8.  
  9. Clinch the upper ears of the outboard shoe by position channel lock pliers with one jaw on the top upper ear and one jaw on the notch on the bottom of the shoe opposite the upper ear. After clinching, the ears are to be flat against the caliper housing.
  10.  
  11. Install the wheel and tire assembly.
  12.  

Bendix Type

See Figures 16 and 17

  1. Remove approximately 1 /3 of the brake fluid from the master cylinder. Discard the used brake fluid.
  2.  
  3. Jack up your vehicle and support it with jackstands.
  4.  
  5. Push the piston back into its bore. This can be done by using a C-clamp.
  6.  



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Fig. Fig. 16: Bendix front disc brake assembly



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Fig. Fig. 17: Removing the caliper support key

  1. Remove the bolt at the caliper support key. Use a brass drift pin to remove the key and spring.
  2.  
  3. Tie the caliper out of the way with a piece of wire. Be careful not to damage the brake line.
  4.  
  5. Remove the inner shoe from the rear caliper support. Discard the inner shoe clip. Remove the outer shoe.
  6.  
  7. To install, lubricate the caliper support and support spring, with silicone.
  8.  
  9. Install a NEW inboard shoe clip in the steering knuckle or rear support. Install the lower end of the inboard shoe into the groove provided in the steering knuckle or support (against the spring clip). Slide the upper end of the shoe into position. Be sure the clip remains in position.
  10.  
  11. Position the outboard shoe in the caliper with the ears at the top of the shoe over the caliper ears and the tab at the bottom of the shoe engaged in the caliper cutout. If assembly is difficult, a C-clamp may be used. Be careful not to mar the lining.
  12.  
  13. With both shoes installed, lift up the caliper and rest the bottom edge of the outboard lining on the outer edge of the brake disc to make sure there is no clearance between the tab at the bottom of the outboard shoe and caliper abutment. The outboard shoe should fit tightly in the caliper and should not rattle.
  14.  
  15. Position the caliper over the brake disc, guiding the upper caliper groove onto the mating surface of the steering knuckle (or rear support) and lower caliper support. Position the caliper to the lower steering knuckle (or support) sliding surface.
  16.  
  17. Place the spring over the caliper support key, install the assembly between the steering knuckle (or rear support) and lower caliper groove. Tap into place until the key retaining screw can be installed, using a brass punch and a light hammer.
  18.  
  19. Install the screw and torque to 12-18 ft. lbs. The boss must not fit fully into the circular cutout in the key. Install the wheel and tire and add brake fluid as necessary.
  20.  

 
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