I have a question. What happens when you put 90w in a posi rear end? I have a noise in I think the diff and it only happens when turning while in gear. If I put it in nutral while turning, it's quiet. But otherwise, it sounds like old bones grinding. I was told that it was probably the Spindle berings, but after replacing one side, I still get the same noise. I really don't think that was the problem. Plus, the berings I pulled out were in excellent shape. Anyone have an idea what this could be? I ask about the diff fluid, because I'm not sure what's in it.