I'm having problems with my diff in GTO again. It was replaced under warranty Dec 2007. Well now I'm having the same problems again with the clunking and howling. Changed the fluid, still the same thing. So I'm going to tackle this, to see whats up with it. Is there any service manuals that cover the specs of the diff, backlash, ect? The GM service manual covers very little about the diff. Also what special tools I need?