New to the boards, have a question.

[crazyhorse]

The flexplate will rattle regardless of it being in gear. It's bolted to the back of the crankshaft. Some people still call it a flywheel. This isn't accurate, but if your mechanic understands that term, it gets the point across. No big deal on mis-naming the part.

Get the car back in the air & check all your heat shields, and ensure nothing is wrapped up in the driveshaft. Basically just look for anything obviously out of place. Start simple & cheap, then work your way up.