How many of us are there? Owners of Dodge based RV's?

goreds2 wrote:

Today, I took it out on the open highway and at about 55 MPH it was shaking.

The very first place I would look is wheel balance. The wheel and tire are a very large rotating mass, and if not balanced right can cause shaking at specific speeds. Usually highway speeds. The other possible cause to look at is tire separation, or being out of round. Once you have eliminated those two possible causes, look at suspension and shocks.
Good luck, and I hope it's an easy fix. :)