Weird Vibration!

Phil I believe Robbie was referring to the driveshaft being his problem. As soon as I was reading your description I was thinking the same thing. It's also possible that it's a tire out of balance.

It sounds like more of an out of balance issue than a bad bearing. Bearings usually howl before they vibrate. Vibrating is the next to the last stage of failure. Last would be locking up or grenading. If it's not howling I doubt it's a bearing.