Heads up if you're getting a strange squeek...
 

Just thought I'd put this out there for anyone that my have had the same problems I just had. I was getting a real bad squeeking (like some jumping on a bed with a bad mattress) when I'd back up. Found that it was the very back universal joint on the back at the end of the drive shaft. Fixed it and the noise went away going back, but then started going front. There's 6 universal joints on the truck (3 on the back drive shaft and 3 in the front, mine's 4x4). So I assumed it was one of the other 2 in the back. Replaced both of those, still did it. Turned out to be the center bearing b/w the 2 sections of the rear drive shaft. All of this is an easy fix. Universal joints are about $12-$13 each and the center bearing part was about $100. Will warn you though...use a cutting wheel to get the old joints out, and if you don't have a press to put the new ones in....be prepared to ruin an impact socket with a mini sledge after beating on it for about a hour to get in so you put the clip on.