I installed new shoes on the rear of a 96 dodge ram 4 months ago. I also replaced both rear wheel cylinders and flushed what looked like the original fluid. The truck ran fine for the last four months. Now:

If the truck has been sitting, and you go to move it, the first two times or so you apply the brakes both rear wheels will lock up a bit. After that they opperate normally? I'm perplexed!!!

 

bump

 

It seems as if there is too much pressure in the line going to the rear. Possibly a blockage, maybe the fluid is fouled somehow? I'd go ahead and bleed out the lines again and add new fluid and see if it does the same thing. It won't cost you more than a couple of hours and some brake fluid. Plus, it will rule that out as the issue.

Is there a brake booster just for the rear wheels on that truck?

 

I'll try bleeding them again. The old fluid was pretty nasty so it is very possible that there is a partial blockage from flushing it. I did a gravity bleed before, I'll hook up a power bleeder this time to hopefully clean it out better.

only one booster on the truck