A paranoid 'rear end noise' thread

So I went to full synthetic for all the diffs and trans case and had noticed a whining noise coming from the rear diff when it is underload. Sometimes I cant hear it at all, typically it is noticible while going up a hill. If I let off the gas it goes away immediately.

I know I put enough fluid back in, is that typical with syn or should I be going back to a dino fluid?

PS this is a TRD OR and I did not put lsd additive in.

 

Rear end noise while on the gas, goes away when you let off the gas. I'm curious, did it make the noise before or after the fluid change?

 

100% sure it's rear diff? A LOT of things can create noise.