I have a 2008 XJ-8 and have noticed a shimmy and a vibration in the steering column when I drive over a rough road service such as a small pothole, a manhole cover or a bumby road surface. I had a Road Force Balancing done but that did not help. There is definitely no balancing problem because the vehicle drives great on smooth surfaces. There is no shimmy or vibration either on non bumpy surfaces at any speed. Allignment seems to be fine. Any ideas? I've read other threads with similar problems with other models but there is no clear answer to what might be causing this problem. I've had a 2002 XJ Sport, 2007 S-Type R, a 2009 XF, and I've not experienced this shimmy and vibration in any of these vehicles.