interesting, yet my parents(moms) 01 pulls great up hills without a redline needed, sits right at about 2200 rpms and just seems like the trailer is not even there. I wonder if something was wrong with the trucks you mentioned... there trailer is right at 20k. The only standard diesel I have towed with was a 94 powerstroke 5spd non turbo... so thats my only comparison..... I really would like to try out a zf truck, when i am in the market again some day that will be what im looking for! they sure are hard to find last weekend i hit up all the lots with trucks with no luck... not that i will be buying of course but really wanted to test one...