Any half decent mechanic should be able to identify the source for the noise. We can't troubleshoot any better over the Internet. Something like a bad bearing may still work for a while.It may be the transaxle, but I'm not convinced. I think the key to remember is that it's still running fine, other than the noise. If the transaxle was toast, as chrysler claims, then that wouldn't be the case.
And I'm still curious how sparks came up with $9k... maybe someone should contact them about this thread.
As for the price quote, I would certainly asked for the parts and labor breakdown and what the labor hours are based on. Not only out of a curiousity, but for practical reasons- in my state the total price work is taxed on the whole amount, while only the parts are taxed on an itemized invoice. This alone could save $300.