My Camaro has a SPEC stage 3, stock T56, Spohn HD driveshaft, and a Moser 12 bolt. I bought the car with a broken torque arm mount (didn't know it til later on), and other than what felt like play in the drivetrain, everything felt fine. After a while, that broken mount really broke and hit the pinion yoke (which was some fun) and I replaced the mount and pinion yoke. Wow, did the drivetrain feel tighter.

Ok, enough on the background, a little while after replacing those pieces I started to notice that 6th gear was a little wierd sometimes. Coasting, everything was fine, and giving decent throttle was fine, but giving just a little throttle (about enough to maintain cruising speed), there is what feels like grinding or roughness and I can't place where it is exactly, but I'm guessing it's in the tranny. Lately, it's been getting worse and it's starting to show up with decent throttle, so I figure I better do something about it. I've figured I just need to rebuild the transmission since it has other issues as well, but before I do, I figure I better be sure it's not something else.

 

You can do what I just did and get a rebuit T56 from T56rebuilds.com. I payed just $1950 ($500 core charge) for a completely rebuilt and strengthened (700 hp) T56. I love it, shifts great (especially with the Pro 5.0 shifter).