Auto Transmission 7AT Rattle at low Rpm's

370Zfeeler

A week ago, my car started having this weird sound coming from the bottom, it would make this rattling noise at around 1.2-1.5k RPM (every time i would stop and go, and when the trans shifts) from 1.5k rpm's up it would go away, at the beginning, thought my FI exhaust may had become loose from one of the hangers, so today I took it to the exhaust shop and noticed everything was ok with the exhaust, checked all bolts, all hangers, everything.

As we studied the sound, found out it was coming from inside the transmission, right where it meets with the engine, its a rattle between 1.2-1.5k RPM's, after that it would go away, you can replicate it by bumping the revs in the low range and also if you hit the brakes and gas at the same time you can replicate the sound continuously. Seems exactly like what the MT guys refer to as clutch chatter.

Transmission shifts perfectly find, everything works as it's supposed to, manual and auto mode, except for the rattling which is very annoying while cruising because the engine speed is around 1.3-1.5RPM's, every time you'd stop and go and when it shifts in the low rpm's. Have any ideas??