Apart from fuel economy, GM's new Hydra-Matic 8L90 transmission also improves the 2015 Chevrolet Corvette Stingray's 0-60 acceleration time to 3.7 seconds, making it run the quarter-mile in 11.9 seconds. Yeah, technology!
The with the eight-speed is EPA-rated at 16 mpg in the city, 29 mpg on the highway and 20 mpg combined (up 1 MPG from the 2014 model). GM went as far as pointing out that the (estimated) highway figure is not only better than of the Corvette's competitors, but also makes the Stingray more economical than a Subaru Outback six-cylinder (27 mpg) or a Volkswagen Passat six-cylinder (28 mpg). Cylinder-deactivation certainly helps.
The improvements are mostly due to the eight-speed's 7.0 overall gear ratio spread, which allows for a more aggressive first gear ratio – 4.56 vs. 4.03 on the six-speed – improving acceleration. That is combined with a new, lower 2.41 rear axle ratio vs. the 2.56 gear used with previous six-speed automatic, which reduces engine rpm by 8 percent (123 rpm) on the highway at 70 mph. GM says the new box "also delivers world-class shift times that rival the best dual-clutch design".
The Z51-equipped models will retain a 2.73 rear axle ratio.