Shake, Rattle, and Roll

I own a 1992 Chrystler Grand Voyager, which I purchased used 3 years ago. When I first got the car, I would hit a dip in the road and here a clunk, still happens. Within the past year my car started to shake, at first it wasn?t so bad. Now is a lot worse. I notice that when I am accelerating the car shakes, the harder I press on the gas the more it shakes. When I release my foot off the gas and coast it doesn?t shake. I just feel like the car is falling apart. I have changed motor mounts, struts, and steering rack and pinion. What could cause this to shake? My dad has no clue. :? Need advice to fix my car!