2015 Chevy Silverado 1500 Brings 8-Speed Auto to GM Full-size Trucks

The General will join Ford and Ram in offering an eight-speed automatic transmission for its full-size trucks this year, pairing a "Hydra-Matic 8L90" unit with GM's 6.2-liter V8 in the 2015 Chevy Silverado 1500, GMC Sierra and GMC Yukon/Yukon XL Denali. 

Developed in-house by GM engineers, the new transmission should result in increased fuel-economy ratings—which will be released closer to the vehicles' on-sale dates—with better off-the-line performance when under a heavy load. It's also worth noting that, even with the extra gears, the 8L90 retains roughly the same size and weight as its predecessor. And it still enables the 2015 Chevy Silverado 1500 and friends to enjoy a max tow rating of up to 12,000 lbs. (per the new SAE J2807 criteria) and the benefits of cylinder deactivation to boost fuel efficiency under lighter loads.

Now, on the topic of fuel economy, we can set a baseline by reporting that the current Silverado gets 15 mpg city/21 mpg highway/17 mpg combined with a six-speed autobox and the 6.2-liter V8 that, by the way, makes 420 hp and 460 lb.-ft. of torque. The F-150's similarly sized V8, also with a six-speed, tops out at 13/18/15; the Ram 2014 Ram's 5.7-liter HEMI, when mated to an eight-speed automatic transmission, can post an EPA line of 15/22/17. Obviously, any boost in fuel efficiency would leave the 2015 Chevy Silverado 1500 ahead of its similarly configured 2014 rivals. But the thing is, with the F-150 going on a drastic diet for the new model year, and the diesel-powered Ram already up to 28 mpg highway, all three top truck entries could be showing their fuel-economy success stories for 2015.

Another inevitability: Look for that eight-speed transmission to migrate throughout the rest of the GM truck lineup sooner rather than later.