GM's Full-Size Pickups Offer Allison Five-Speed

GM’s 2001 full-size pickup trucks that are equipped with the 8.1-liter Vortec or 6.6-liter
Duramax diesel will be available this fall with the M74 option, which is an Allison
heavy-duty five-speed automatic transmission. When descending a grade, the Allison’s engine
braking system calculates the weight of the truck’s load, its speed, and rate of
deceleration. It then selects the proper gear for the situation and automatically
downshifts if necessary. This feature is especially helpful for trailerists.