I have this strange vibration coming from underneath the car (an '06 auto GT). I feel it pretty much only when letting off the throttle or when braking over rough surfaces or manholes. It doesn't seem to be an issue when I'm accelerating. It is not really audible but I can feel it through the pedals. The source of it seems to be underneath the car, directly under the center of the dash I would guess.

I'd describe it as a rattle - sort of like when you're cold and your teeth chatter. Or like when you're riding a ten speed bicycle and you don't shift right and the chain hasn't locked into the next gear yet (but is still in motion). I did some research and I heard of something called "gear chatter", which seems to fit this description pretty well. Has anyone had experience with this?

I've been to Ford and their tech can't seem to identify the problem.

 

trans, u-bolts or driveshaft possibly

 

I think Ford has a TSB out on your exact problem. Take it to the dealer, not to mention you should still be under warranty. If you have ANY problems whatsoever, take it to the dealer and make them deal with it. Your car is brand new there shouldnt be ANYTHING wrong with it. And sometimes, even if the problem isnt covered under warranty the service manager has an alloted "good will" amount that they sometimes will cover repairs under.
-P.

 

Is the TSB you mention the one regarding the transmission bell housing?