Thanks for the suggestions. I took it back to the service place and the foreman looked at it. Turns out it was the driveshaft hanger. Probably got knocked around when they were doing the parking brake.
All is well, except that the vibration seems to have caused some sort of grounding issue that is affecting the radio and CB. I am now hearing significant alternator whine especially on AM radio. The alternator is charging fine, but I am guessing some ground is faulty somewhere.