I am at my wits end with the rear end of my 2011 GT. I have had rear end whine problems with all 3 of my new s197s.
This one started when i noticed a pinion bearing noise on deceleration at a couple thousand miles. They replaced the pinion bearing. but after that the rear end whined at highway speeds. I brought it in where they replaced the ring and pinion. Well it still made noise so they replaced them again. It was perfectly quiet for a week and then it came back. I seriously just think that the technician just doesn't know how to get the gear pattern correct. I paid 37k for a car that the rear end it louder then a Mack truck. So damn annoying. I recently moved from Kansas back to Florida and I am looking into bringing it back to a competent dealer if anyone knows of one.
I also had the windshield replaced due to a crack at 2500 miles and ever since the windshield has whistled. I've had it back two sperate times and it's still there sometimes.