ball joints or tie rod? pitman arm? My friend had a similar prob. in his grand cherokee. It had a broken mount somewhere that was supposed to connect the axle to the chassi (i never actually saw it, so i can't describe it that well). If it's a tj, then i would check for this. Even if it's not a tj, i would reccommend jacking the front up, checking for steering free-play, and watching the steering, suspension, and front end componets while someone is behind the wheel steering. It sounds like something is slipping/sticking when there is alot of lateral force on the tires.