I don't know what the problem, but it sounds exactly like what my GTS was doing before I parked it a few years ago, but mine did have a pull, too. Depending on how hard you hit the brakes, it would pull one way or the other. The brakes grab and sing. I've decided to go disc brakes on the car and will probably go through the suspension as the last time I did it was 1986 and about 70,000 miles ago. Basically, check EVERYTHING.