The 2015-MY Chevrolet Silverado 1500 will have 11 percent greater torque capacity than the previous model thanks to its all-new GM-developed Hydra-Matic 8L90 eight-speed transmission, according to the automaker.
Matched with the 6.2L EcoTec3 V-8 engine, the 2015-MY Chevrolet Silverado will produce 420 hp and 460 lb.-ft. of torque. The truck's EPA-estimated fuel economy will be announced closer to the start of production in the fourth quarter of 2014. The truck has begun arriving at dealerships.
With four simple gearsets for optimal efficiency and five clutches (two brake clutches and three rotating clutches), creative packaging enables the new eight-speed automatic to fit the same space as the previous six-speed automatic, with a lower weight. A wider 7.0 overall gear ratio spread provides a numerically higher 4.56 first gear ratio, helping drivers start off more confidently with a heavy load or when trailering, according to the company.
The 2015 Silverado 1500 equipped with the 6.2L engine and eight-speed automatic transmission will have a maximum available trailer rating of 12,000 pounds, based on the SAE J2807 towing standard.
Smaller steps between gears, compared to the 6L80 (see chart below), keep the engine within the sweet spot of the rpm band, making the most of its horsepower and torque to optimize performance and efficiency, according to the automaker. They also enable numerically lower rear axle ratios, which reduce engine rpm on the highway for reduced fuel consumption.
Additionally, friction-reducing design features – including all-new synthetic fluid – and lower spin losses via a powerflow that uses only two open clutches contribute further to efficiency. A new torque converter design with turbine damper enhances refinement, particularly during low-speed gear changes, for smoother performance when the truck is loaded or pulling a trailer.
Ratios compared: Hydra-Matic 8L90 vs. 6L80
8L90 eight-speed automatic
6L80 six-speed automatic
Gear ratios (:1)
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