Well, today I decided I'd drive my 69 Charger to work, its an hour drive one way. All was good cruising at 75 80 then as I approached a construction zone I down shifted, and the Charger went into a massive vibrating fit. The vibration seem to be more calm at 55mph so I limped the rest of the way to work then straight back home. I have not had a chance to inspect but I'm suspecting U Joints. What do you guys think it is?