I have a grinding noise in the steering at very low speeds (pulling out of a parking space). Dealer has now replaced rack and pinion 3 times and noise returns after about 1 week. Cadillac technical support now says they will not replace this part again and noise should be considered "normal". Started at about 47,000 miles. Now at 50,000. This is a CTS performance AWD vehicle. Any ideas on other soultions?