I have an '85 3/4 ton (4x4) with the heavy duty brake package. I get the same problem nearly every time I park the truck after driving in the wet. Next time I go to leave I get the rear wheels locking up solid the first one or two times I apply the brakes. I'm usually just pulling out to the drive at the time so no real speed involved but they come on with a real bang and stop the wheels dead. I've got fairly old shoes in there and was thinking that might be a factor. I've already tried replacing the wheel cylinders and the master cylinder is also fairly new. Any help much appreciated. By the way after the first couple of applications everything works fine.
[updated:LAST EDITED ON Jan-31-04 AT 07:16 AM (CST)]Proportioning valaes tend to be expensive and don't generality fail. So, befor I invested in one I would check out the brake lines and parking brake cable frist. See that the cable is moving freeley and look for anything that would cause a restriction in fluid movement. If there is nothing obvious, i would change the rubber brake line or lines going to the rear wheels. My felling is that something is keeping some pressure on the rear brakes. You wont tend to fell this problem when moving forward like you would when backing up. When you solve this problem please let us know what you found. I am not getting older I am getting wiser. FrankC
