[rverdlm]

As I said weigh the truck loaded and air the tires to the correct level for that load from a tire chart. Your ride will improve dramatically. Go here and you'll see what I mean http://www.goodyear.com/rv/pdf/rv_inflation.pdf
It shows that at 50psi you're still rated at over 8000# for your rear axle and I doubt you're that heavy.