From a cold start while in park the idle is smooth no vibrations at all. When shifting to reverse there's a gear moving (possible grinding) sound in the back and when slowly moving (reversing foot on the break) there are vibrations that can be felt in the wheel and seat and are somewhat audible. The same thing happens in first if purposely driving slowly like in reverse.
The car is an 2008 mustang V6 with 27,000 miles on it. Some help trouble shooting or possibility's what is is would be great, its under warranty still.
Thank you.

 

How do you manage to have a 2008 still under warranty? Do you mean an extended warranty?

The 4.0 may simply have a harmonic at low rpm's. IIRC, my wife's 4.0 has a little shake at some low rpm.

 

Its under the original (know the dealership ford owner) but its bumper to bumper still. I dont know its its something i should get checked out or what and yeah thats how mine is.