Yep, pretty normal. Aftermarket shifter will help on noise and there is a guy selling a gasket set that is supposed to help quite a bit as well (cobrabob).
Yes, they are noisy. I took mine in as well, and they said it was fine. When I went to pick it up, they drove me around in a new '04 Cobra on the lot, and it did the same thing.
Adds to the uniqueness of the machine. When I did the Richard Petty Nascar Experience their tranny made a lot of the sounds the t56 does. Makes me feel like im in a race car with every thump, crackle , and pop.
I know to add strength to gearing different champfers and angles are used and the straighter the gear, the noisier they are (my old procharger comes to mind.) MMFF says they never have broke a T56, if the noise is a result of strength, wonderful.
It does not bother me as long as I know it is normal. Now that I do, THANK YOU.