I had a 2008 GMC Dually and put a B&D electronic variable vein brake on. It was the best thing I did to that truck. Going down 8 - 10 % grades if I would set the speed at 25 mph it would not go past 27 mph. I traded it in on a 2015 dually chevy, and the exhaust break is piece of junk inless I do not know how to work it because it always goes 7-8 mph faster than I want I hate it.