A replaced both U-joints on the rear shaft about a month and a half ago. Only the one closer to the differential was bad, but I figured I'd get them both out of the way while I had the shaft pulled out.
Well it seemed to fix my clunk during initial acceleration right away, which was good because the jerking force from it went away as well.
After about a couple weeks however, it seemed to slowly come back. Now it is just as bad as it was prior to replacing them. I do do a lot of four wheeling though.

Does this sound like normal wear time given the driving conditions of four wheeling and such?

Note- I do have a 4 inch suspension lift, so I know that kills the lift out of it a little faster. A month just seems a little premature to me though.

 

Did you use new joints with grease fittings? If so, hit them with a shot of EP grease.

 

It may not be the universal joints. There is a issue with some of these trucks where the main driveshaft front spline hangs up momentarly upon accelleration The drive shaft is suppose to slide back and forth where it enters the transmission. If you remove the shaft you will see the female spline that is inserted into the trans tail piece. Clean this spline out with brake cleaner or equivelant. Then apply Teflon grease ( dealer carries it) into the female spline of the driveshaft. There is a TSB for this issue.This usually prevents this condition for a while but it will probably come back. I have removed and lubed mine several times and it still comes back. Annoying but not detremental to the truck. After you removed the driveshaft to install new universal joints you probably got some trans oil in the shaft spline and it prevented the problem from happening for a while. Good luck.