Truck Repair: 1996GMC3500HD Pulls to R when braking, gmc 3500hd, brake hoses

Question
My 1996 GMC 3500HD pulls hard to the right when braking.  I just replaced both front calipers (the left side was frozen), but it still pulls.  When I slam on the brakes on gravel, the right front tire locks up, and leaves a skid mark.  Could there be a problem with some type of proportioning valve in the abs unit? please help!!!

Answer
there could be a problem with the abs. first on your front brake hoses where they go to the caliper they have a clamp to keep them from rubbing.try pulling the clamp apart. they will rust and collapse the lines.one of them could also have a flap inside restricting the flow.easy thing to do is replace them if they aren't expensive.thanks for the question.