I have a loud clumping noise when shifting my 03 Hemi Ram 4x4 into reverse. It doesn't happen when shifting into drive. I thought maybe the rear U-joint was going bad. I climbed under the truck and there's play in the drive shaft. When I rotate the drive shaft there's a clunk in either direction right where the shaft meets the rear end. I know nothing about rear ends whatsoever and could use some help from someone that does. I'm adding a pic of a rear end, and there's an arrow pointing to where the clunking sound comes from. Any help is greatly appreciated.

 

I have basically the same truck as you and mine has made that clunk for longer than I can remember. I changed out all my tranny fluid and filter and it still does it. Filters and oil were clean with very little debris in the pan.

I think its just nature of the beast being the first year hemi and that transmission. I've never had problems with my tranny. I've noticed that shifting into reverse while the truck is slowly rolling forward will remove the clunk sound.

 

Download and read the Service Manual for "driveline clunk". It will tell you everything you need to know and what possible problems it can be.

When I had it on my rear differential, it was because the pinion nut and backed off a little allowing the pinion to move on its own