Q&A

 Master

Front end shake (brakes not applied) at 50 to 65 MPH is usually wheel imbalance. You could try rotating the tires yourself and re-drive the Caravan and see if the problem changes or goes away. Check the condition of the tires perhaps you have a badly worn tire. If after rotating the tires the problem doesn't change the front suspension needs to be inspected for wear. Could be worn shocks or suspension bushings.
If the "roughness" is experienced on acceleration could it be an engine misfire you are experiencing?

happend to my 92 standard caravan replaced wheel bearings and was back to normal

believe it or not it might be the engine mounts. I have a 94 caravan and this happened to me. The engine sags and the front axles aren't at the right angles anymore and essentially start twisting the wheels up and down. The rubber just wears out and the engine drops down relative to the wheel axles.