hi all, new guy here. i just traded a junky 91 camaro for this 93 chevy 1500 shortbed. the driver's side front wheel is locking up and it woun't move very well. the p.o. said he thought it was the caliper. so i bought a reman cailper and replaced it, bleed the brakes, no differance. so i replaced the master cylinder ,blead it, no differance. so what could it be ,the porportioning valve ?