So my brother has an 02 F250 extended cab with the 7.3 (4x4)
I drove it the other day and it has a wicked vibration. He said that speed doesn't really have any effect on it. Typically happens over 50mph, but is not limited to a certain speed.
The center console whips back and forth.
I couldn't feel it in the steering wheel, but could feel it in the seat and floor board which would typically mean the rear of the vehicle.
Where do you think we should start looking? U-joints?
He said he had 1 u-joint replaced recently, but I don't remember which one.