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

I have been loving this thread going on 7 years now when I had my 1975 Class C. I now have (for 5 years) a 1989 Dodge XPLORER RV Class B with 318 engine. Today, I took it out on the open highway and at about 55 MPH it was shaking. I know it can be a number of things but just wondering if any owners of late 80's Dodges have experienced this. Thanks,

Note that I checked the tire pressure and they are read the same. (50-PSI)