The new 6.7-liter Cummins I6 turbodiesel produces a whopping 350 hp and 650 lb-ft of torque. It also has emissions controls, including catalytic converters. Do the emissions controls adversely affect performance? We'll see. This engine is so quiet that some people think there's a gasoline mill under the hood. You can even let it run in drive-thru bank and fast-food windows. Seat-of-the-pants performance seems to be better than the 5.9 it replaced. The six-speed automatic has two overdrive gears and a column switch that allows complete control over what gear you're in. The factory exhaust brake gives even greater control over braking.