I am new to this site and just bought my first CTS V . I have a 2012 with an automatic and at low speeds turning either direction I get this terrible howl sound from the back of the car. I bought this from an original owner and has been dealer serviced since new. The car is extremely clean and completely bone stock with 67,000 miles. I bought the car out of state and had it shipped to me only to find out I have this problem. The dealer just did a differential service 11,000 miles ago. Any advice would be greatly appreciated.