My F250 was pulling one way then the other, all winter. Well, turns out the brake calipers were sticking. I have just turned over 100,000 miles on this 2000 truck. The calipers were not just sticking, 2 [ drivers front & passenger rear] were flat stuck. After all new calipers, new pads and 1 new rotor , this darn truck rolls and my fuel mileage has really improved. If my truck did it, I'm sure there are other trucks out there that have the same problem. It just gradually sneaks up on you, and you don't think of it as a brake problem. If your old Ford ain't what she used to be, check those calipers.