I have a 2000 F-550 with a rear end floating or sway feeling. It's a mason dump body and has 4x4. The org Generals and stock Ford shocks have been swithed to Bridgestones and Monores. Dealer and spring shop were unable to find problem. It seems like the truck is loaded heavy when empty. At hi-way speeds this is quite discomferting. Truck is used to plow with but has minute mount disconect plow so most of it is off the truck so I dont think its a weight on the front end issue. It has only about 40,000 miles on it and only hauls heavy loads once in a while but when it does its at the capicity of the truck. Rear was destroyed and rebuilt by dealer once, trany was worked on at least 2-3 times also done at dealer. It was sugested to me that I lower tire PSI by about 10 pounds as this cured a simular problem with school busses were I work but because I load truck to capacity this fix makes me a tad nervous. THANX