OK, so here is my problem. At approx 50 miles/hour when I decelerate I get a loud gear whine, I believe I hear it at other times but not very noticeable. During acceleration I hear nothing. Also there is quite abit of slop in the yoke going into the dif.
As to the cause, I hit a curb at about 40 - 50 M/h awhile back and it broke the control arm and the right rear disc. So it was quite the hit on that half shaft.
Anybody have any ideas what could be causing this whine? Seems unlikely it would be gears to me as I don't feel any slip in the rear. Feels like a bad bearing but there is too much slop in the yoke.

 

If it was gear whine, you would hear it most of the time. Not really sure what it could be, but I had a similar wreck with a 97gt which bent my left axle. It was eating my rotor up due to the bent axle.

Also take a look at your U-Joint, and check your Differential oil making sure that is evenly filled with the opening.

 

Oil is fine. I believe it is the bearing. I just hope it isn't spun.