this is called "death wobble," a common problem in Jeeps and some 4x4 trucks. The bad part is that once you have it, it never really goes away no matter what you do. The good news is that a heavy duty steering stabilizer will usually control it. Be certain that your front tires are balanced and not flat spotted. Sway bars only control body roll on turns, and will not affect death wobble one way or the other.
Sometimes altering the caster on a front end alignment job helps as well. Note that lift kits will alter caster by changing the angle of the entire truck as well as the front axle.
01 QC, totaled.
Early 04, 6 speed, power everything. Stock. so far.