What would cause the rear drum brakes to lock up upon hard braking? I have replaced the wheel cylinders, installed new spring kit, and adjusters.

 

The year of your truck would help.

 

it is a 1989 lariot 4 wheel drive

 

Your truck should have RABS. Have you disabled it? Is that ABS light on the dash lit up? Does it come on briefly when you start the truck?

 

Yes, the light comes on briefly then goes out.

 

It could be the RABS valve itself. When the brake fluid isn't changed regularly, it absorbs water and corrodes the inside of the valve. When you release the brakes, the springs should cause the shoes to back off but if the valve is gummed up they stay engaged. This causes them to heat up and stick. Another possibility is that the axle seals are leaking fluid and have contaminated the shoes. This will also cause them to stick. Lastly, are you sure you put them back on correctly? Incorrectly assembled brakes can also stick sometimes.

 

They have been sticking after hard braking for a while. I am certain all was reassembled correctly. Can the abs valve be cleaned or should it just be replaced.

 

I would try re-adjusting the brakes. Remove the drums. Pull the adjuster lever away from the adjusting screw star wheel just far enough to disengage it. Rotate the star wheel to expand the brakes far enough so the drum can be installed with a slight drag, then loosen the star wheel 2 turns to retract the shoes.

 

I would bypass the RABS valve altogether. It has several cons (softer pedal feel, another bleeder screw to mess with, clogged up valves cause rear brakes to stick) and no pros. The RABS doesn't work that well to begin with.

 

I will try that. Thanks for all of your help, my 16 year old son who is getting this pick up also thanks you!