Gears & Axles - Rear end noise question?

I have this whinning noice when I make a left turn, and only a left turn. It is coming from the rear. I had a guy back home that works on rear ends and he says that he doesn't see anything wrong with mine. I don't know what it might be, so if anybody has an idea then please tell me. :bang:

I had this when i used conventional gear oil without the posi additive. Even though my differential doesnt need the additive, adding it quieted it down. Moving back to synthetic along with the additive elimitaned the noise.