Just to elaborate on what’s already been said……..Did this start to happen immediately after you replaced the pads? If so, it may be due to the fact that one of the calipers is starting to seize up. When you pushed the caliper pistons back to make room for the new pads, did it take a lot of force? More force on one side than the other? Brake fluid is hydroscopic ( likes to absorb water) , so if the brake fluid has never been changed, it may be that corrosion has started to take place inside your calipers. The caliper can function normally, because the piston gradually moves outwards as the pads wear, and then when you push the pistons back in, the corrosion starts to jam up the piston. The piston may not be totally seized, but if one piston takes more force to move than the other…. as in if the left piston is sticking, more force will be applied to the right rotor and you’re truck will pull to the right. Another possible scenario is that if you’re right caliper is starting to seize, the piston isn’t releasing properly and dragging against the rotor…causing the pull to the right. (although in this case, the pull will usually continue for a short time after you release the brake pedal.) As previously mentioned by FC, make sure that there isn’t any slop in the wheel bearings. Try bleeding the brakes, just for good measure…new fluid can’t hurt. As well as what’s mentioned above, you could raise the front end off the ground, apply the brakes hard and then try turning each front wheel to see if one wheel is dragging more than the other. Malfunctioning rear brakes will have an effect, but based on you’re description (pulls badly), I would say that the problem is in the front.
