I have had this problem with all three of my Chevy’s I owned. 85 caprice, 88 c2500 silverado, and the 79 blazer. One of the back wheels will lock up on gravel at low speed by just tapping the brake petal. On the caprice, the left rear would do it for a few days then a week later the other one would do it. Both the truck, blazer would, will occasionally lock a rear wheel at medium brake pressure. Not both, just one wheel. It seems most likely to happen with quick applying of the brakes. I'd hate for that to happen on a high speed corner... not to mention I just bought new Michelin tires for the back, and they cost pretty penny. I know shocks can help traction, but this is not hard braking. Thanks in advance.

First check the adjustment. Over adjusting will cause this. Also check the hardware (springs, adjuster, cable, hold downs, etc.) and backing plate. Worn out springs and a rusty backing plate can cause the shoes to stick and not self center when released. It could also be a pressure problem. I.E. restricted line or leaking wheel cylinder. Does the problem only happen at certain times? (In the morning, rain, or hot weather.) My 1995 C-30 had a horrible problem with rear noise when the humidity was high.

Thanks for the reply. Will open it up. It doesn't happen much, the left rear is doing it once in a while when you're going 10 mph or less when you're going staight or turning left and you jab the brakes. Not a panic stop, just half way.