The Stovebolt Site Forums The Shop Area General Truck Talk Rear brakes locking up

You did not say if you have disc/drum or disc/disc.
Since your MC is below the wheel cylinders or close to it, you probably need residual valves. Most kits will come with 2 lb for front and 10 lb for rear. (disc/drum). It could have come with a built in proportioning and porting for what you have. Adjustable valves are sometimes recommended. Refer to your instructions, double check your plumbing and contact vendor. If it was doing it before change over I would suspect weak return springs or other malfunction inside brake drum. Should replace all parts in there. Shoes need to contact stop boss when brake released. If you had too much pressure in rear it would do that but you can't have too much with a 10 lb residual or no residual. If you have a adjustable maybe it's set wrong. Otherwise it has to be bad/missing parts inside drum..... If you have disc/disc, different story involved.