If you think the 2500 is slow, Budget truck rental had the 4.8 and 4-spd in their 16 ft. box trucks from 2005 and on until the 6-spd was released...can't imagine being fully loaded and towing a car over a huge pass. Spent a lot of time driving those empty and they were dogs down low. Suprised GM even offered the 4.8 in that configuration, the 5.4 in the Ford felt like a powerhouse in comparison.4.8L 2500 Express with a 4L80E.....Totally mismatched combination & an absolute dog. I've done several 5.3L & 6.0L swaps on these after the 4.8L broke a valve spring, Dropped the valve & disintegrated a piston. They have to spend so much time at or near redline that the valve springs take quite the beating.