my friend has an 01 F150 that seemed to have some of the same problems. it would literally feel like it was going to shake apart and made the worst sound. for him it ended up having to do with the exhaust system.
Ask yourself whether the dream of heaven and greatness should be waiting for us in our graves - or whether it should be ours here and now and on this earth.
Dan's College doesn't pay for itself: http://prontocuts.com