I had a '95 TT Supra that made chattering transmission noises when starting off from a stop. Mechanics told me it was normal. Then I had a 2002 corvette (bought new) that made the same noises. Dealer said it was normal. Drove it for 9 years with no issues. Now, I have an '11 Nismo that makes the same noises. I've convinced myself that it's all normal.