i have a 1992 dodge d150 318 auto trans. when i start it up either the engine or something vibrates at maybe 1500-1800 rpms. this just started a few days ago while on the freeway i can feel my whole truck vibrate. also there is a very small clunk when i put it in reverse
i replaced the u joints this summer rebuilt trans 1 year ago
i do beat on my truck from time to time any ideas??

 

the clunk might be the low oil level in the rear axle.

 

I would check the u-joints again. It is possible that when you replaced the u-joints one of the bearings might have fallen into the bottom of the cup. Another problem I have had is with the u-joint strap bolts loosening up. I now use lock tight to prevent this.