My 96 f150 4x4 is almost un manageable at 40+ mph,especially if its a rough bumpy road, it was recently aligned so im not sure what to check. It doesnt like to stay straight and air pressure is fine, possibly power steering pump not bled right? Also its got 6" of lift with 35s, any ideas? Adjust steering box?

 

Its not the lift I know for a fact. My buddy has a 93 with the same lift and tires, and he has no problem steering.

 

You'll have to check for play in the steering system. It could be the steering box, have a helper rock the steering wheel and see if that translates from the steering shaft to the pitman arm. If you do adjust the worm gear preload, do small amounts like 1/8 to 1/4 of a turn at a time.

Theoretically a shop would not have aligned it if there was play in the tie rod or drag link, or ball joints.

There's no way to say your lift is not partially to blame without knowing details. ERA's or no? How were the TTB arm pivot bushings? Also wheel width is a huge factor, I'd personally never run a 15x10 on TTB; 15x8 is the max IMO assuming a 35x12.50. And of course you did install a drop pitman arm, yes?

 

Every truck is different so saying the lift has nothing to with it is naive. A lift always messes with geometry and they usually have not been engineered to make every little detail work as it should. As with any old truck, steering u joints are probably worn as are most things regarding handling. Also a lift sometimes doesn't accommodate for steering except usually a pitman arm. I would check all linkage and make sure nothing is loose.