Ford 2001 Explorer sport

It could be a loose steering box. The pulling to the right or left may have masked the slop by always preloading the gear in that direction. Might also be some worn steering linkage that was masked too. If the toe-in is not enough it will wander.

Best of luck

Chances are not likely. Usually the amount of inbalance is not all that noticeable to most people and it usually just screws up the tire wear. Is your wheel alignment a possibility. A dragging brake could be a cause.