1998 Chevrolet Truck Repair Question
Rear brake clunking
Double-check the adjustment first. I have the best luck adjusting them up by hand, then trying to slip the drum on. If you use a spoon to reach through the adjustment opening when the drum is already on, often one shoe makes contact first and produces enough drag to give the false impression both are adjusted up enough.
Another common cause is a parking brake cable that is stuck partially applied. Both shoes must be touching the large anchor pin at the top of the backing plate. You should also be able to move the parking brake strut bar against the anti-rattle spring pressure when you push it by hand. If you can't, the cable is sticking.
Be sure the longer lining is toward the rear of the truck and the shorter one is toward the front.
Finally, look for grooves worn into the backing plate. There's six "lands" the shoes ride on. They should have a dab of high-temperature brake grease on them when the shoes are replaced. Failure to lube them results in grooves that can cause the shoes to bind and not apply under light pedal pressure, and in severe cases, not release smoothly.
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OK, I removed the brake shoes and my truck dosen't call for a longer pad to go in the back. But I did notice that one shoe pad was offset when rivited in place. Got a replacement set of shoes from autozone and they where all indentical. Installed them and no more clunking. Thanks for the help.
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Interesting. When you have the extremely common duo-servo drum brakes, the front lining's job is to grab the rotating drum, try to spin with it, and it pushes the bottom of the rear shoe into the drum. The rear piston in the wheel cylinder pushes the top of the rear shoe into the drum. The rear lining is longer because it's the one that actually does most of the stopping. The clue is the movable lower connection, (typically the star wheel adjuster).
Many smaller cars have a fixed lower anchor riveted to the bottom of the backing plate. On those, just the front shoe applies when driving forward, and it wears out much faster than the rear shoe. Those shoes are usually the same length and can be switched front-to-rear.
I suppose it's possible your front and rear shoes are the same length but that's not what I would have expected to find. The proof would be found by comparing your old shoes. Regardless, I'm happy to hear the noise is gone.
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