I pull my 3580RL with a modified F250 PSD. I have installed an oversized transmission cooler, a pyrometer, a boost guage, a transmission temp guage, a 5" exhaust system, a severe "Donaldson" air cleaner system, Firestone air bags, Super sways, diablo 85 HP chip, superbuild transmission, 10 ply Toyo Tires, oversized shocks, bypass engine oil system, synthetic oil (both trans and engine) and a few more smaller items. I can feel it behind but since adding the super sways, the wind does not knock me around anymore. I have owned 3 dual rear wheel trucks and the only beneift I have found is, well none. Most will say it is more stable, but with super sways there is no differance. I will tell you that my milage was always worse with a dual rear truck.