It has been known for some time now that Chevrolet was working on an eight-speed transmission for use in the new Corvette Stingray, and on Wednesday, the company was gracious enough to share the details of its new unit, lovingly dubbed the Hydra-Matic 8L90 paddle-shift eight-speed automatic transmission, which will see action on the 2015 model year Corvettes and Corvette Z06s.
Off the bat, it’s safe to say that this unit was built to be used and abused, implied merely by its installation in the 650 horsepower and 650 pound-foot Z06. The party piece, however, is that by offering eight gears, the transmission will allow the Corvette (not the Z06, though, most likely) to achieve 29 miles per gallon on the highway. You know, in the ballpark that many mid-size sedans are playing in.
“GM’s new 8L90 eight-speed automatic represents a rare win-win-win scenario for customers,” said Kavoos Kaveh, global chief engineer for eight-speed automatic transmissions in the company’s press statement. “It offers greater performance and efficiency, while weighing less than the transmission it replaces. That’s a rare accomplishment in the industry today — and one for which GM has been awarded more than two dozen patents.”
The unit uses four simple gearsets for efficiency purposes, working in conjunction with five clutches (two-brake clutches and three rotating clutches). Despite the two extra speeds, the 8L90 was developed to occupy the same real estate left vacant by the outgoing six-speed. Extensive use of aluminum and magnesium will also make it more than eight pounds lighter than the outgoing unit too, GM said.
As you would expect, there are also some significant performance gains to be had with the eight-speed, should you choose to go with an automatic. The top gear ratio is 0.65 contrasted with the six-speed’s 0.67, GM said, adding that, “Combined with a new, numerically lower 2.41 rear axle ratio in the Stingray vs. the 2.56 gear used with previous six-speed automatic models, engine rpm is reduced by 8 percent (123 rpm) on the highway at 70 mph.” It noted that the lower engine speed helps cut fuel consumption, while a new torque converter design “enhances refinement, particularly during low-speed gear changes.”
Owners of the Corvette equipped with the Z51 Performance Package will be treated to a more aggressive 2.73 axle ratio, while the Corvette Z06 features the 2.41 axle ratio. The 8L90 uses a new Gen II transmission controller, which analyzes and executes commands 160 times per second, and wide-open throttle upshifts are executed up to eight-hundredths of a second quicker than those of the dual-clutch transmission offered in the Porsche 911, GM claims.
At the end of the day, the transmission will allow the ‘Vette to hustle to 60 in just 3.7 seconds (if equipped with the Z51 performance package). That’s within a breath of the Porsche 911 Turbo’s 3.2 seconds, and actually faster than the 911 Carrera S. The 16 mile per gallon city rating, 29 highway, and 20 combined is for the standard model, Autoblog was able to confirm.
The 8L90 “was designed to enhance the driving experience, with performance on par with dual-clutch designs, but without sacrificing refinement,” Kaveh said. The biggest question now is: do you sacrifice the tactile feeling of the manual for the latest and greatest piece of transmission engineering?