Dealer and LSD Problem

jpit

I noticed that when making a tight turn (close to the steering lock) that my 2009feels as if it is going over bumps in the road. My warranty expires in April so I decided to have the dealer take a look at it. They called back and said that the differential fluid needed changing and it "would only cost about $200." I had changed to Redline about 10,000 miles ago and knew this probably wasn't the problem. I told them that I would change the fluid myself (if I had a lift this procedure would cost $20 and take 15 min.) When I picked it up they said they went ahead and changed the fluid anyway and added additives and would put it under warranty. They then confirmed that the problem still existed. Told me to drive it for 100 miles and bring it back if it doesn't clear up. I told them that I thought the LSD in the 370Z was actually a sealed unit inside the differential casing and additives probably wouldn't help. I don't think they believed me. Anyone else have this problem?