car has a noise/vibration coming from the front floor hump at highway speed. Dealer & GM field personnel have changed the transmission , exhaust system, motor mounts and wheel bearings. Noise is still there after 5 weeks at the dealer. GM is taking the car back to the engineering dept for evaluation. I will not be getting it back regardless. Another Lucerne (3.9) at the same dealer has the identical problem. I have asked for a replacement with the 4.6 V8 engine or a full refund. Mt recommendation was to have the NVH engineering guys identify the root cause and then have the appropriate product engineering guys fix it. I am a retired engineer and we solved issues like this in a few hours.
comfort & ride. Not noise from the drive train !
Use the correct technical support to resolve issues such as mine.