A quick way to check - jack up one rear wheel at a time, and rotate the wheel.  With the suspension basically on full droop you'll be making the cv joint work at it's maximum.  Also, after PLACING A JACK STAND UNDER THE VEHICLE, lie down and eyeball the cv boot as you turn the wheel.
You might like to check the torque mounts ( the North and South engine mounts)  If you can rock the engine backwards and forwards by hand, that's not good.
After these simple checks, if you can't see anything wrong, I'd start to think "gearbox internals".
Best of luck, and I hope it's something simple.