Buyers have the choice of two powertrains. GM isn’t spilling the beans on the new direct-injected gasoline engine, but it’s rumored to be a Navistar-sourced 6.6-liter V-8 from MD Trucks. This engine will come paired to a six-speed automatic transmission. The other option is a Duramax turbo-diesel V-8 that pairs to a 10-speed Allison automatic and delivers 910 lb-ft of torque.