I had the same kind of problem and it turned out to be an out of balanced radiator fan, take your fan belts off and see if the vibration goes away. If it does, the problem is the fan blade, water pump or alternator. Something that the belts are driving. It's also possible to have an out of balance harmonic balancer but not likely.

Last edited by dmerc; 10/25/08 09:04 AM.