One of the most talked about features on the 2015 Corvette Z06 is the new high performance 8-speed automatic transmission.
It was back in May of 2011 that we first learned that GM was developing an eight-speed automatic transmission for its high performance cars. But one of the things we didn’t know was that the Hydra-Matic 8L90 would be designed from the ground up specifically to handle the more than 635 lb-ft of torque generated by the 2015 Corvette Z06.
To make sure the new transmission was compact and light enough to fit into the Z06, engineers worked to remove mass while maintaining strength and durability. Plus, it had to work well the with new Gen 5 engine’s cylinder deactivations.
The new 8-speed transmission weighs 8 pounds less than its 6-speed predecessor and it offers a 5 percent better fuel economy than the previous six-speed automatic. Despite its small package, it can handle up to 738 lb-ft of torque.
Bill Goodrich, assistant chief engineer, 8-speed RWD transmissions told Engine Technology Now “Where we have low-stress areas on parts, we’ve cast, stamped or machined holes in them to remove unnecessary mass, while maintaining strength in the critical areas.”
The use of materials also played a key roll in mass reduction. The gearset carrier is made of aluminum, the clutch piston housing is made of magnesium. Steel is used where high stress areas need it the most.
“The transmission is made up of four separate gearsets and five clutches,” says Goodrich. “A key feature is that in every gear state we have three of the five clutches applied; with only two open, you minimize the drag and spin losses you get from an open clutch pack.”
In developing the Hydra-Matic 8L90 automatic transmission, the engineers benchmarked the Porsche 911’s PDK transmission and they claim to have matched or beaten those shift times through a combination of hardware and software.
While the new Hydra-Matic 8L90 transmission will first see action in the 2015 Corvette Z06, we can only hope that this next generation transmission will see duty in the Stingray in the near future as well.
Engine Technology Now