grinding sound at 45+

i have a 4.0 ax15 np 231 and a 8.25 and most of the time when i'm on the gas at about 45 to about 65 i get this grinding sound. i have looked at u joints they don't have any play that i can see but the rear driveshaft can turn more then i feel is normal.also when i shift i get a clunk from what sounds like the rear end. if you guys have any ideas that would help alot. thanks

U-joints,they can feel tight but be plenty bad!