The TSB does not seem to be for the problem described by the OP. It is a "groaning/creaking suspension type noise" heard when going slowly over speed bumps. Not a whine as in the TSB. Haven't seen a TSB for this for 2011-2012.
I have had the same problem on my new 2011 GT. It only happens when going over speed bumps so I just live with it until I can take time off work to take it to the dealer to have it checked out (much as I hate to). I don't think it is normal and will probably not go away. Seems to come mostly from the passenger front.
I would be really interested in knowing if anyone had actually taken the car to the dealer for this and what was done.
Originally Posted by Blacksmoke
Check out this TSB.
It says for 05-10 Mustangs but they might just not have updated it to include the 12's.
Click this link: