I just bought a 2010 Camaro RS 2SS with an auto transmission. The car only has 2900 miles on it and I knew the previous owner and it was never beat on. It did sit for years at a time however. The only issue I have is the rear end makes a groaning noise when I turn sharp at low speeds. Going straight it sounds perfect. I took it to a local performance shop and they said the rear end lube was probably broke down and needed changed, so they did and added a friction modifier.It still sounds the same and they said it would take awhile to get into the posi unit and calm things down. Is that correct or is there more problems?

 

5th gen limited slip rearends have clutches, so it's possible the old lube was broken down, or gut gummy from age and lack of use, causing the clutches to stick and chatter around turns. What the performance shop did is the first logical step to see if that is in fact the cause. You need to really work the new lube into the clutches. Take the car to an open parking lot and do a lot of slow figure-8's, until you start to feel nauseous. See if that helps it get any better/quieter.