Larry: I'm sorry to hear you are still having problems. Have you talked with Prevost factory personell in Quebec. They would apt to have more answers to that kind of problem. I guess they had all of your tires and wheels off and balanced them. I don't recall your mileage. It is possible some driveline damage could be causing the problem. With all the aligators along the road (truck tire re-caps) these can cause real damage if kicked up under our coaches. I hope other Poggers weigh in here with more insight to your problem.
Harry
Shirley & Harry / 2000 Liberty / 2008 GMC Envoy Denali