Alright as some may have saw my old thread about my cars shutter issue when turning from a stop or very low speed. Well I took it into Ford again finally (different dealer) and they looked at the car and informed me that my differential is the heavy duty carbon diff found in the Track Pack option. Now from my understanding the C/S cars didn't have that as an option? I even checked my vin and there was indication on the window sticker of it having it either simply stated the standard rear with 3.15 gears. Is it possible the previous owner swapped the rear diff in? According to the dealer its not uncommon for that rear end to shutter like that. They even showed me this service bullentin stating so: 2011-14 Mustang GT equipped with BREMBO brake package. These vehicles are equipped with a heavy duty/racing carbon fiber clutches in the LSD. This type of LSD may exhibit a chatter or moan/groan noise when making sharp low speed turns. These noises are a normal characteristic of the heavy duty/racing type LSD. Note: Driving the vehicle in a tight figure eight pattern 5 times may lessen the complaint for a short period of time. My car does not have brembo brakes which is why I was curious plus the window sticker states nothing. Yet the dealer said it does have it because that's what they saw when they looked at the rear diff and opened it up.