I was driving my 09 Cts-4 w/ 20,000 miles on 12-12-09 @ 40 mph when I heard a loud boom from the rear and the rear wheels locked. This caused a huge jerk and several skips on the road before coming to rest after a 150 ft skid (paced off skid marks). When I tried to drive the car from it's stuck position from the middle of the road, the exact same thing occurred @ 5 mph. The car was towed to a dealer. GM authorized the dealer to replace the rear differential assembly under warranty sight unseen. The dealer did not even remove the differential first to determine the damage or diagnose the cause. The service manager said there was no sign of fluid leakage and that the differential was full of fluid when it was removed. The differential has been replaced and there has been no problem since. Fortunately the car did not skid off the road. Had other cars been on the road, a crash would have occurred.

- Lawrenceville, NJ, USA

When driving a 2009 Cadillac Cts the car generates a drone, boom and vibration. This happens when accelerating to or driving at highway speeds. I bought the car new and there has been a problem has been with this car since I took delivery from the Cadillac dealer. GM has issued a service bulletin (#08-07-30-044B) to install rubber insulators and reprogram the transmission control module. This "fix" did not help. It only moved the onset of the vibration to a higher RPM/speed. When the vibration occurs the car does not feel safe. I am not sure if a mechanical component is going to fail. The drone is constant, distracting and annoying while driving. There is also a boom noise at 5 mph when coming to a stop. This is not a smooth quiet safe car. The Cadillac service mgr says he does not hear anything. I do not agree. Cadillac also says the noises are inherent in the vehicle and have no fix. They are making no attempt to fix the car at this time.

- Elmont, NY, USA