Inspect the brake shoes for peeling, cracking or extremely uneven wear on the lining. Check the lining thickness using calipers. If the brake lining is damaged or worn within 1 / 32 in. of the rivet heads on riveted linings, the shoes must be replaced. The shoes must also be replaced if the linings are contaminated with brake fluid or grease. Always replace brake shoes in axle sets. Never replace just one shoe of a brake assembly.
Check the condition of the brake shoes, brake springs and drums for signs of overheating. If the shoes have a slight blue coloring, indicating overheating, the brake springs should be replaced. Overheated springs lose their tension and could allow the new shoes to drag and wear prematurely, if not replaced.
REMOVAL & INSTALLATION
See Figures 1 through 12
- Raise and safely support the vehicle. Remove the rear wheel and tire assemblies. Remove the brake drum.
- Remove the shoe-to-anchor springs and unhook the cable eye from the anchor pin. Remove the anchor pin plate.
- Remove the shoe hold-down springs, shoes, adjusting screw, pivot nut, socket and automatic adjustment parts.
- Remove the parking brake link, spring and retainer. Disconnect the parking brake cable from the parking brake lever.
- After removing the rear brake secondary shoe, disassemble the parking brake lever from the shoe by removing the retaining clip and spring washer.
- Before installing the rear brake shoes, assemble the parking brake lever to the secondary shoe and secure it with the spring washer and retaining clip.
- Apply a light coating of caliper slide grease at the points where the brake shoes contact the backing plate. Be careful not to get any lubricant on the brake linings.
- Position the brake shoes on the backing plate. The primary shoe with the short lining faces the front of the vehicle, the secondary shoe with the long lining, to the rear. Secure the assembly with the hold-down springs. Install the parking brake link, spring and retainer. Back off the parking brake adjustment, then connect the parking brake cable to the parking brake lever.
- Install the anchor pin plate on the anchor pin. Place the cable eye over the anchor pin with the crimped side toward the drum. Install the primary shoe-to-anchor spring.
- Install the cable guide on the secondary shoe web with the flanged hole fitted into the hole in the secondary shoe web. Thread the cable around the cable guide groove.
The cable must be positioned in the groove and not between the guide and the shoe web.
- Install the secondary shoe-to-anchor spring. Make sure the cable eye is not cocked or binding on the anchor pin when installed. All parts should be flat on the anchor pin.
- Apply a thin coat of lubricant to the threads and the socket end of the adjusting screw. Turn the adjusting screw into the adjusting pivot nut to the limit of the threads, then back off 1 / 2 turn.
Make sure the socket end of the adjusting screw is stamped with an R or L, indicating the right or left side of the vehicle. The adjusting screw assemblies must be installed on the correct side for proper brake shoe adjustment.
- Place the adjusting socket on the screw and install the assembly between the shoe ends with the adjusting screw toothed wheel nearest the secondary shoe.
- Hook the cable hook into the hole in the adjusting lever. The adjusting levers are stamped with an R or L to indicate their installation on the right or left side.
- Position the hooked end of the adjuster spring completely into the large hole in the primary shoe web. Connect the loop end of the spring to the adjuster lever hole.
- Pull the adjuster lever, cable and automatic adjuster spring down and toward the rear, engaging the pivot hook in the large hole of the secondary shoe web.
- After installation, check the action of the adjuster by pulling the cable between the cable guide and the adjuster lever toward the secondary shoe web, far enough to lift the lever past a tooth on the adjusting screw wheel. The lever should snap into position behind the next tooth, and the release of the cable should cause the adjuster spring to return the lever to its original position. This return action of the lever will turn the adjusting screw one tooth.
- If pulling the cable does not produce the action described in Step 17, or if the lever action is sluggish instead of positive and sharp, check the position of the lever on the adjusting screw toothed wheel.
- With the brake in a vertical position (anchor at the top), the lever should contact the adjusting wheel 3 / 16 in. above the centerline of the screw. If the contact point is below this centerline, the lever will not lock on the teeth in the adjusting screw wheel, and the screw will not be turned.
Adjust the brake shoes as explained in this Section, then proceed as follows to determine the cause of this condition:
- Make sure that the upper or anchor pin end of the cable is pulled toward the cable guide as far as possible and that the end fitting is pointing toward the cable guide.
- Check the cable end fittings. The cable should completely fill or extend slightly beyond the crimped section of the fittings. If it does not meet this specification, possible damage is indicated and the cable assembly should be replaced.
- Check the cable length. Measure from the inside edge of the hook to the far edge of the anchor hole. The cable length is 11 in. (28cm).
- Check the cable guide for damage. The cable groove should be parallel to the shoe web, and the body of the guide should lie flat against the web. Replace the guide if it shows damage.
- Check the pivot hook on the lever. The hook surfaces should be square with the body of the lever for proper pivoting. Replace the lever if the hook shows damage.
- Make sure that the adjusting screw socket is properly seated in the notch in the shoe web.
- Make sure the upper ends of the brake shoes are seated against the anchor pin and the shoes are centered on the backing plate. If they are not seated, back off the parking brake system adjustment to obtain 0.005-0.025 in. (0.127-0.635mm) play after overcoming the load of the parking brake link spring.
Whenever the brake shoes are removed, the parking brake cable adjustment should be checked.
- Make sure the brake shoes are properly adjusted, then install the brake drum and wheel and tire assemblies and lower the vehicle.
- Apply the brakes several times while backing up the vehicle. After each stop, the vehicle must be moved forward.
- Check brake operation by making several stops from varying forward speeds.