General Motors is confident its new 8L90 eight-speed transmission, which will debut in the 2015 Corvette Z06, will be the final piece of the puzzle that will edge the Corvette into an EPA-certified 30-mpg highway fuel efficiency rating, according to a report from the Society of Automotive Engineers.
“No comment—but we’re giving the vehicle team a ratio spread of seven that’s wider than the current 6-speed and will be useful in improving overall efficiency,” said Kavoos Kaveh, GM’s Powertrain Global Chief Engineer for 6 and 8-speed automatic transmissions.
Even though the 8L90 transmission was designed for use in the 2015 Z06, lead Corvette engineer Tadge Jucheter previously confirmed it will find its way into other applications eventually. Many assumed the standard Corvette Stingray would adopt the eight-speed transmission this year to coincide with the launch of the Z06, but Juechter has hinted more towards the standard car adopting the new unit for the 2016 model year.
“We’re very close to 30-mpg with the 6-speed car, so two extra ratios is something we like very much,” said Juechter.
GM says the eight-speed transmission improves the Corvette’s efficiency by up to 5 percent compared to the 6L80 six-speed currently in the Corvette Stingray. The unit is over 8lb lighter than the six-speed it replaces, while being equivalent in overall size. Engineers say it shifts 0.08 seconds quicker than the lightning-fast dual-clutch transmission in the Porsche 911 when under wide-open throttle, while a deeper first gear ratio improves launch capability.