i have a similar problem with my rig (99 yukon) not sure what it could be. on one of the motorcoaches i drove this summer had a death wobble on it that puzzled the mechanics and annoyed the drivers (it shook the entire thing) eventually, pat (our mechanic) took it apart and found the spindle was bent, prolly from a hard hit on the road. it was bent by .03 in, just enough not to be noticed earlier. replaced spindle, problem gone. you might check into that. i know that right now i dont have the money to buy those parts to fix it, maybe when the cv joints crap out, then ill just put a solid axle under it. hope this helps