I am toying at the idea of going to a 4500 or 5500 with a camper bed and storage. I hear how bad they ride empty without something like a liquid spring setup ( Im sure that costs a small fortune). I have been hearing that the only difference may be the spring pack and the axles but then someone looked at the springs and counted and they were the same. Not that you could tell a rate difference, but the dealer told him put in the optional 4.88 on the 4500 and you have a 5500....hmmm