I agree with this:
T45....bad gears.
3650...bad synchros
T56 barely handling the power the 03 Cobra's make
I haven't heard of any breaking. They are handling some serious power as far as I know. I decided to go with the Viper spec T56 though...handles more power, and only a couple hundred more than the other T56's on the market.
My 2 cents.