Rob,
Our first RV was a 22' Four Winds on a Chevy 3500 (1 Ton) truck chassis.
When we first got it, the ride was like yours, TERRIBLE!!! We actually had silverware bounce out of the drawer and broke glassware in the cabinet.
One day, I crawled underneath and looked at the spring stack on the rear axle.
The 13 leaves of the spring stack were absolutely FLAT. There was NO arch in the springs. When striking a bump, the rear axle could NOT move UP to absorb the blow.
The air in the rear tires was the ONLY suspension that there was. The axle housing was still 2 inches from the rubber bump stops (POOR design).
I ordered a set of 5,000 lb. capacity Air-Lift air bags (about $200) and installed them myself in a couple of hours. I didn't even have to jack up the body to get them installed. I ran the air inlet tubes to a storage bay.
When I added 55 pounds of air (about 1/2 full) the body actually rose up 1-1/2 inches. Now I had 1-1/2 inches of Tire, spring, and air bag travel.
The bags made it an ENTIRELY new RV. It was wonderful!
Later on, I added Bilstein shocks to the FRONT in order to stabilize and eliminate the "porpoising" on that end.
In the end, the ride was FANTACTIC!!! The ride was almost as good as that of my 3-seat GMC Suburban.
When we upgaded to a 28 ft. Coachmen Freelander, it came with Air-Lift air bags installed at the factory. I have never had to add air to them to use them.
I suggest that you or a shop-guy look at the rear spring stack to see whether or not you have any, or adequate, rear axle UP-travel.
Tim
