I have this noise in the rear end. Its a lound clank. When I shift from reverse to drive and back and forth. Its a automatic transmission. I had the gears replaced 3 years ago. I hoping its not a sound of the rear going bad. Someone told me that its the universal joint but when I has it looked at they couldn't find anything. Has anyone ever heard of this.

 

Did you look at the pinion nut? This could loosen. Usually u joints going bad make that sort of noise, as when they go bad the joints get really stiff and pop back and forth rather than smoothly.