Its a 92 P/U 4x4 5sp, when the clunking happens is whenever I go around turns or whenever the rear tires go up over a bump (It doesnt have to be a large bump) almost like the rear springs are worn out, but the truck willl level itself out in 1-2 bounces so whenever I stand on the bumper and jump up and down so and there is no sagging so the rear suspension seems alright.
Its not a real loud clunk, but its not faint either. The driveshaft U-Joints all seem alright, no free play there and they have just been lubricated.
The only thing that has been done to the truck recently is an undercoating, so I figured maybe something came loose, but everything seems tight.
There are no suspension or body lifts to the truck yet, it is completely stock just for info, but im really stuck on the origin of this noise. I know that the rear end clunks going around turns when it is worn out, but I didnt think it clunked going over bumps, I could be wrong on that. Also, I just changed the rear end fluid and there were no metal chunks or shavings in the old fluid, and im fairly sure the rear end is in good shape.
Any help/suggestions would be appreciated because im kind of stuck and I hate any unusual sounds coming from my Truck, Thanks

 

A good set of shocks should level the truck out within 1 bounce.

Any play in the rear end?

loose shocks?

are you SURE its the rear end?

I had a similar problem, everytime I go over bumps I hear a loud CLANK, turns out its my tailgate floppin around.

 

hmm, I never thought of the tailgate, Ill take it off tommorow and see what happens, It seems to loud for that though.

 

check the shocks. they could be worn out.

 

You can test the tailgate by taking a hold of it, pulling up and then trying to move it around.

like 881stgenRunner said, make sure the shocks are not blown, they could be floppin around, also make sure they are tightened down properly