GM Large Trucks to Get Standard 8-Speed Automatic

General Motors Co. will make its Hydra-Matic 8L90 8-speed automatic transmission standard on 2015 model Chevrolet Silverado and GMC Sierra fullsize pickup trucks and GMC Yukon Denali SUVs.

The transmission will be paired with the company's 6.2-liter, 420-hp V-8 engine. The gearbox replaces the current 6L80 6-speed automatic. GM says the new unit is about the same size and weight.

The 8L90's two additional gears will provide more low-end pulling power at startup and enable a taller rear-axle ratio to lower engine speed on the highway. GM will announce federal fuel economy ratings for the new powertrain shortly before the system goes into production late this year.