Thats what always struck me as weird about the older Macs, a straight 5 or 6 speed in em, Mack engines myst be real torque monsters or the truck itself is a real dog when fully loaded. Always looking out for a deal to build another grain truck. Have one with a DT466 and a straight 7 speed, that one doesn’t do too bad, the old truck has a 3208 and a 13 speed. I prefer the International semi tractor with a 9 speed, can’t remember which Cat it has but it’s more than torquey enough, have gone across the scales at cargo with 92,000 gross.