General Motors said a new Hydra-Matic eight-speed automatic transmission will be standard on 2015 Chevrolet Silverado and GMC Sierra pickups, and in GMC Yukon Denali and Yukon XL Denali SUVs equipped with the 6.2-liter EcoTec3 V-8.
The Hydra-Matic 8L90 eight-speed is approximately the same size and weight as the 6L80 six-speed automatic, an announcement said, but has a wider 7.0 overall gear ratio spread. It includes a numerically higher 1st gear ratio for surer starts with a heavy load or when trailering, and allows numerically lower axle ratios, which reduce engine rpm at highway speeds.
With 420 horsepower and 460 pound-feet of torque, the 6.2L EcoTec3 V-8 is the most powerful engine offered in any light-duty pickup, GM said, and offers a maximum trailer-tow rating of 12,000 pounds, based on SAE J2807 test procedures.
As with other EcoTec3 engines, it switches to four-cylinder operation under light loads to improve fuel economy. Additional technical details and EPA estimated fuel economy figures will be announced closer to the start of production in the fourth quarter of 2014.