1984 GMC 3/4 ton. Disc front, drum rear. I had to get on the brakes hard the other night, and ever since then, the rear's have been locking up really bad with only a little pedal pressure. They look fine when the drums are off. The proportioning valve, I assume, is stuck or not working properly. Is it adjustable, because I don't see any way to adjust or bleed it. I called my dad and he said there should be a bleeder on it, but there isn't that I can see. There is a little rubber thing on the end like a primer for a lawn mower, but no adjustment screws or bleeder screws. Gonna try to bleed it by loosening the lines, hell, it can't get any worse than it is now...any ideas would be great! Thanks...

And this is non-caddy, so it should be alright here! :D

And my damned chiltons for this truck is in Imperial, NE... :(

Go here and register, if you own a Chevy, it's the #1 site!!:thumbsup:

where is that?!

You can try to press the button to re-center the valve. If it really is the problem, resetting it will cure your problem. Chances are the problem may be glazed shoes though. You may have to pull the drums and scuff-up the shoes with some sandpaper to fix the problem. Also possible is that on some trucks there's a metering valve in the rear that adjusts the rear braking power based on the suspension compression. This valve might be your problem.

I guess the link would help!!:bonkers:

http://www.chevytalk.org/threads/ubbthreads.php