After skipping the 2008 model year, with 2007 being the last for the GMT800 hybrid line, a two-mode hybrid model was introduced in late 2008 as a 2009 model. General Motors discontinued the Silverado Hybrid due to poor sales along with the GMC Sierra Hybrid, Chevy Avalanche, Chevy Tahoe Hybrid, GMC Yukon Hybrid, Cadillac Escalade Hybrid, and Cadillac Escalade EXT after the 2013 model year even though it was the one of the two first hybrid pickup trucks ever manufactured. Available in either two- or four-wheel-drive, the Sierra 1500 Hybrid is powered by a 6.0-liter V8. It's joined by two 60-kilowatt electric motors supplied by a nickel–metal hydride battery pack under the rear seat. On its own, the V8 is rated at 332 horsepower and 367 pound-feet of torque. GM engineers say that combined output with the electric motors is 379 hp. The unique transmission houses the electric motors along with three different planetary gear sets and four traditional clutches.