Ok, I'm going to humiliate myself publicly but I think, maybe someone else has my experience level or less working on their truck. Mine is a '90 K5, 4" RC all-sprung lift with 33" Pro Comp M/T's (none of which matters with this problem). I had a nasty vibe so went to change the rear u-joint on the rear driveshaft. I've done u-joints before, or helped with them at least. So Monday I did the job. Tuesday night I went to work and it was shaking worse than ever. On the way home the joint snapped and also the shaft was dented and bent slightly in the process. I just put the shaft back on now. Still in my greasy coveralls as a matter of fact /forums/images/graemlins/grin.gif What I did wrong is this: I thought the straps that hold the u-joint to the rear pinion yoke were what held the u-joint in place (do I hear laughing??). They don't. And, rather than tabs that hold the u-joint in, mine has c-clips that come with the u-joint, that hold it in. So that's what those were for!! I have to go across town to pick hubby up from work in a bit here, so I'll know better how much vibe I have from the damage. I went up and down the road, heavy on the skinny pedal, and it held fine. Hope that helps someone.