Chevrolet Repair: Chevy Silverado 01-Braking issue, chevy silverado, anchor pin

Question
Van,

I hope you can help, as you are the only one available that may be able to help me out. After releasing the brake(pedal)when at a complete stop and waiting for at least 20 seconds, I hear and feel a thump or knock comming from my brake pedal. It only happens when I first drive the truck after it has been parked. Transmission fluid is fine and engages fine when I accelerate.I had to take it in to the dealer 1 year ago for a gasket replacement for the transmission and a couple of other items(can't recall at this time).It has only 57K on it.Thanks.

Answer
Hello Mike,
Here is a guess.
If one of the rear shoes, upon release of the brakes, does not go all the way released with the end of the shoe settling back against the backing plate anchor pin. Like maybe it is catching or sticking a little. Then it slips off whatever it was sticking on, and returns to the full released position, it could force a little fluid back into the master cyl.
Or the master cylinder piston or power booster is doing a similar thing, like the vacuum booster staying just slightly applied, and then releasing when the stuck piston releases.

Van