Faster shifting, lighter weight Corvette gearbox goes the torque converter route
Chevrolet has officially revealed the new 8L90 eight-speed automatic transmission destined for duty in the 2015 Corvette. The 6.2-liter V8/eight-speed combo is good for a 0-60 time of 3.7 seconds, 29 mpg and faster shifts than many dual-clutch transmissions -- most notably the one found in the Porsche 911.
We tested the 2015 Corvette on General Motors' famous Milford Road Course test track and the streets surrounding. We're not going to say the new automatic is better than a manual transmission; it isn’t. There’s still no way it can match the involvement or control of rowing your own gears. But we can say with authority that a dual-clutch isn’t the only way to go if you insist on letting the car shift itself.
Chevy went with the torque-converter automatic over a dual-clutch for a few reasons: The DCTs on the market wouldn’t fit in the space reserved for the 2014’s six-speed, and it also works better with the Corvette’s Active Fuel Management system that helps get that 29-mpg EPA estimate.
The 8L90 weighs about 8 pounds less than the outgoing six-speed automatic thanks to extensive use of magnesium and aluminum. A taller top gear leads to an 8 percent decrease in engine rpm at 70 mph.
Out on the roller coaster that is the Milford Road Course, we threw the Corvette into track mode, tossed in our SD cards for the Performance Data Recorders and left the gear shift in D. It takes about two turns and a hard braking event to get the trans to realize you’re on a racetrack, then it switches into what we’ll call “redline mode.” At that point, the transmission kicks into the lowest gear possible at the current speed. It’ll drop down three when you’re on the brakes hard, and hold at high rpms indefinitely if you keep the throttle steady.
PHOTO BY CHEVY
We only caught the new transmission hunting once in about 12 laps on the difficult course, and that could have been our fault with sloppy pedal work -- feathering the gas when we should be flooring it, or the other way around. It is a little unsettling seeing the shift lights on the dash flashing, which means “shift,” while and transmission just hangs in gear and the exhaust wails at full rpm.
Once your driving has settled down off the track, the eight-speed automatically adjusts back into “street mode.”
After driving three high-powered cars with eight-speed, torque-converter automatics (Challenger SRT Hellcat, Jaguar F-Type R and now the Corvette), we can say the newest models are every bit as good as the dual-clutch setups. They can shift as fast, feel smoother and aren’t rough on low-speed launches like many of the performance-oriented DCTs on the market, giving you all of the advantages and none of the disadvantages.
No automatic offers the connected driving experience of a true manual, but they get closer every year; Corvette buyers who want an automatic now have the option of one of the best units on the market today.
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