Brakes are smooth as glass. I feel nothing in the steering wheel.. I rotated the tires with the theory that if one of the rear tires was the culprit I would feel it in the wheel when I put it on the front, but nothing changed..

Another thing that might be of note.. When I accellerate (sp?) quickly through that range of speeds, I really don't noitice the vibration.. It's really noticeable just when cruising...

I had done a little reading, and my wild guess was the center bearing, or center bearing support??? Do they go bad?????

If it were a motor mount, or tranny mount, I wouldn't think it would be so sensitive to vehicle speed.. Only engine speed, and load..