While driving there is a grinding noise

I asked about this but lost where the question went.
While driving noise level is close to none, once you let off the gas there is a grinding noise similar to wheel bearing. If am driving say 50 MPH and I put it in neutral, it goes away. But the noise isn't in the transmission but on the rear right. In general, when that happens what suggestions do you have as possible candidates?
This is the 4S trim AWD.