When i put my DSS one piece it was a bitch to put both clips in but you need the clip on both sides.

 

Yes, that's what did it. From what you had described it sounded like the clips weren't in. When they come from the factory, they don't use a clip. They use heated plastic to hold the caps in. You need to heat the caps so the plastic will loosen and then you can remove the caps. When you didn't heat it, and pressed them out I'm sure you bent the ears, probably to the point where you couldn't get the one clip in. When there was no clip in it, centrifugal force threw the cap out causing it to vibrate. It just got worse from there...

 

That sounds so logical I'm gonna roll with it.

Couple weird things though. This is like the 3rd or 4th set of u joints that truck has had and it's been stock height all its life. Couple that with the driveshaft not having either clip on the rear uoke when I pulled it off. Was that just an extreme case of luck that it went like that for 3 or so years?