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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Saturday, November 5th, 2011 AT 5:56 PM