2015 Z06 8spd Auto "Faster and smoother than any dual-clutch"

"MooseKnuckles" (andyschenk) 01/20/2014 at 09:13 • Filed to: corvette, z06, c7, 8 speed automatic transmission, dual clutch, chevrolet

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!!!error: Indecipherable SUB-paragraph formatting!!! faced a difficult challenge when searching for the proper transmission to be paired with their all-new 625 horsepower supercharged LT4 engine in the !!!error: Indecipherable SUB-paragraph formatting!!! . They wanted to match the lightning fast shifts offered by Porsche's PDK transmission, but no dual clutch existed that simultaneously met their compact size requirements nor could handle the LT4s 635 lb-ft of torque.

The answer? Build one that could. The 8L90 eight-speed automatic transmission found in the new Z06 was developed entirely within GM. It's a traditional automatic gearbox in its design, but GM says it shifts not only faster than any dual-clutch, but smoother as well.

Lead Corvette engineer Tadge Juechter highlighted the stringent packaging requirements the team had to meet for the 8L90.

"It's engineered by GM, internally, and many of the parameters were focused on this car," Juechter told !!!error: Indecipherable SUB-paragraph formatting!!! . "So it's almost a custom transmission."

Juechter explains that the transmission, which offers 5 percent better fuel economy than the equivalent six-speed automatic, was designed to work seamlessly with the Corvette's cylinder deactivation system.

"We wanted a transmission that provided everyday drivability and compatibility with cylinder deactivation," he said. "When you run in four-cylinder mode, a torque converter is really your friend."

Juechter confirmed the transmission will find its way into other applications, even though it's design was influenced solely by the Z06 project.

A key piece of the design in the 8L90 is what GM is calling a "smart pump". Under heavy acceleration, the transmission uses two inlet discharge ports, providing more flow to the clutch packs. When cruising, the system automatically calms down a bit and resorts to a single inlet port, reducing drag.

The 8L90 is designed to be compatible with the standard Corvette Stingray's torque tube, suggesting that it could eventually find its way into the standard car as a rolling update or mid-cycle refresh. The transmission is the same physical size as the existing six-speed automatic, but thanks to a lightweight aluminium and magnesium construction, its eight pounds lighter. Despite the light weight, it can handle up to 738 lb-ft of torque.

The 8L90 has a tall overdrive ratio for seventh and eighth gear (0.86 and 0.65, respectively), while the sixth gear is a direct drive. The new setup also allowed GM to lower the final drive to 2.41 from 2.73, though the taller base axle is still available as an option.

According to MA , GM is still honing in shift patterns, shift points and the map for cylinder deactivation, so official fuel economy figures for the Z06 are still some time away. Between the efficient eight speed transmission, lightweight construction and cylinder deactivation system, the Z06 is shaping up to be one of the most fuel efficient supercars on the market.

Yowen - not necessarily not spaghetti and meatballs > MooseKnuckles 01/20/2014 at 09:22

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SRSLY? EXPOSED FASTNRES??? omgzzz...

EL_ULY > MooseKnuckles 01/20/2014 at 09:24

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Watch out....

radioactive ( insert Z06 competitor )!

speaking of, what would that be exactly?

Z_Stig > MooseKnuckles 01/20/2014 at 09:27

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Smoother? Yes, most definitely

Faster? Puh-lease

duurtlang > MooseKnuckles 01/20/2014 at 09:30

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Interesting. Both faster and smoother? It's only got upsides? There has to be a catch here, somewhere.

Bandit > MooseKnuckles 01/20/2014 at 09:32

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They need to build a million of these so in the future when they are dirt cheap I can swap one into my Trans Am.

Clown Shoe Pilot > MooseKnuckles 01/20/2014 at 10:01

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which end of the torque tube does the torque converter go on?

Storz > MooseKnuckles 01/20/2014 at 10:04

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Amazing

bones > MooseKnuckles 01/20/2014 at 10:31

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i'm not convinced women and homosexuals need to drive a z06...sure, it's gonna have 8 speeds, but so does a blender, and a blender is generally in the kitchen, right where they belong...

MooseKnuckles > EL_ULY 01/20/2014 at 10:42

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Basically anything. 458, 12C, 911(s), Viper, etc.

Victorious Secret > MooseKnuckles 01/20/2014 at 10:50

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I would like to call BULLSHIT.

Faster? Really? Are they saying it rivals the boxes that crack off 50ms or less shifts? Are they really going to say that?

Smoother? Well it better be, it has a torque converter for crying out loud!

But faster? Ehh...

Bullshit.

MooseKnuckles > Victorious Secret 01/20/2014 at 10:58

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Might be some fine print in his claim. Fastest transmission for an 8spd in a car with 600+hp. Something like that, so in 4 months when his claim doesn't hold true he said say "that's what I meant"

SnapUndersteer, Italian Spiderman > Victorious Secret 01/20/2014 at 10:58

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Relax AJ.... Relax and wait until you have all the info to judge

Victorious Secret > SnapUndersteer, Italian Spiderman 01/20/2014 at 11:00

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PFFT AINT NOBODY GOT TIME FO THAT

Victorious Secret > MooseKnuckles 01/20/2014 at 11:02

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Well I could respect blurring the lines and making THAT kind of claim.

He really should've just said "We were way too cheap to develop a DCT that could handle that much power so we went with a torque converter that can be used across GMs portfolio with ease"

I mean, all they had to do was ring up Ferrari and get a hold of their 7 speed DCT that sits in the F12. That thing would've at least been a nice starting point if not the final product for a DCT.

PS9 > Victorious Secret 01/20/2014 at 17:40

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I doubt they would have given it to them. The C7 is what's making the Viper such a tough sell right now (well...that and dickhead dealer markup). Helping improve your competitor's halo product so it can further render your own irrelevant on the marketplace isn't a good look.

I kind of feel bad for GM. They totally missed the DCT boat, but there's almost no one they can partner with for one now. BMW is already going steady with Toyota (who also doesn't have a DCT). There's VAG, but they have no reason to give them one, really. In turn for making you more competitive with us, what do we get? They could partner with one of the bespoke guys (Getrag, ZF, others), but I'm willing to bet the really good stuff is tied up in exclusive licensing deals, as other marquees got their first.

I'm guessing the only way we can see a DCT from GM is if they make one themselves, and if they don't have prototypes out there testing as we speak, then that's still a long ways off. I'm really hoping not though, because a DCT CTS-V would be the balls.