Following suit with its C6 predecessor, the C7 replaces its previous automatic transmission in its second production year. The 2015 Corvette Stingray will offer a nearly identical version of the Z06’s 8-speed automatic transmission – the 8L90. The 8-speed was designed as GM’s answer to the dual clutch transmission of its foreign counterparts.
“Corvette Stingray’s new eight-speed automatic delivers the comfort and drivability of a true automatic transmission, as well as lightning-fast shifts and the manual control that enhance the performance-driving experience,” said Bill Goodrich, assistant chief engineer for eight-speed automatic transmissions. “It was designed to enhance the Stingray’s driving experience, with performance on par with dual-clutch designs, but without sacrificing refinement.”
When compared to the previous six-speed automatic (6L80E), GM says the new 8-speed will boast a 5% improvement in fuel efficiency (EPA test pending). Using four gear sets and five clutches, the 8-speed fits in the same space as the 6-speed automatic, yet is 8 pounds lighter thanks to the use of aluminum and magnesium. However, its real benefit is in performance. By having smaller steps between gears, the 8L90 keeps the engine in its powerband. And shifts are made nearly instantaneously via the steering wheel mounted paddles. A new transmission control system with unique algorithms executes commands at 160 times per second. Wide-open throttle upshifts are made eight-hundredths of a second quicker than the Porsche 911’s DCT.
A unique clutch pack and torque converter separate the Stingray and Z06 version of the 8L90 to better match the powerband and torque capacity. Each 8L90 is built in GM’s Toledo, Ohio transmission facility.