Read article by Larry Printz The Morning Call and Mcall. Com-Say this model is Cadillac's only rear-wheel drive. Is it front or rear wheel drive? Having trouble with sound and vibration from rear and bottoming out in front.
It's rear-wheel-drive but there can be some confusion because it uses half shafts just like all front-wheel-drive cars use. It doesn't have a solid rear axle like cars had in the '60s and '70s.
The symptoms you described can all be caused by weak springs. That will allow the car to sit too low and bottom out easily. It will also change the angles between the cv joints and shafts. That can set up vibrations, especially if there are worn spots inside the inner cv joint housings.