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Thanks to MotorTrend, we have learned:

"Wide open throttle second-to-third upshifts are 0.08 seconds quicker than those of its benchmark, Porsche’s seven-speed PDK, says Kaveh (0.45 vs. 0.53). Downshifts from WOT at 60 mph in Sport mode are just as quick (0.95 seconds) too. The PDK also nips at the Hydra-Matic’s heels during WOT first-to-second upshifts (0.49 vs. 0.52)."

"To experience the gearbox’s character, Chevrolet set us loose on its 2.9-mile twisty, undulating, blind-corner-filled track at the Milford Proving Grounds. Nil-to-wee sprints in Track mode, automatic shifts, were quite telling: The gearbox knocked off gears at its indicated 6500 rpm abruptly, spectacularly, with an accompanying violent explosion that only a 6.2-liter V-8 with quad pipes could produce. As corners neared, downshifts were again crisp. Deep inside corners, gears held with no moments of confusion or hesitation — it was as if the CPU was more intuitive than reactive; more organic than robotic — which ballooned my confidence and allowed me to pinpoint the longish nose."


"While Chevy’s numbers beg to differ, the 8L90 in Track mode simply didn't feel as quick as the PDK when operated via its plastic paddles. Don’t get me wrong, clicking off a WOT upshift is a glorious, stupidly fast affair. It is much the same for downshifts. Yet, Porsche, with its well-honed cohesion of an extra clutch and different structural packaging, still has the upper hand in smoothness and feel while on track. Even still, the 8L90 was impressive, especially when off the track. We drove more than 40 miles in highway and city settings around Milford. Smoothness was the name of its game. Intuitiveness was too. Multi-step highway passes in automatic mode required no pauses on its part. The ‘Vette just flew. Then it calmly upshifted into a gear best suited for casual cruising."

2015 Chevrolet Corvette Stingray Eight-Speed Automatic First Drive



2015 Corvette Stingray eight speed automatic First drive | Autoweek

"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."
 

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2015 Chevrolet Corvette Stingray Eight-Speed Automatic First Drive


"While Chevy’s numbers beg to differ, the 8L90 in Track mode simply didn't feel as quick as the PDK when operated via its plastic paddles. Don’t get me wrong, clicking off a WOT upshift is a glorious, stupidly fast affair. It is much the same for downshifts. Yet, Porsche, with its well-honed cohesion of an extra clutch and different structural packaging, still has the upper hand in smoothness and feel while on track. Even still, the 8L90 was impressive, especially when off the track. We drove more than 40 miles in highway and city settings around Milford. Smoothness was the name of its game. Intuitiveness was too. Multi-step highway passes in automatic mode required no pauses on its part. The ‘Vette just flew. Then it calmly upshifted into a gear best suited for casual cruising."

But get this: It’s also quicker. In fact, the 8L90-equipped Stingray is quickest Corvette in a straight line (until the Z06 arrives) with a 0-60 mph dash in 3.7 seconds and quarter-mile run 11.9 seconds (no word on trap speed). Added Juechter: “(Those times) should be easily replicated. We’ve had cars in the 3.6s — even some cars in the 3.5s, but we’re going to market with the 3.7 as the performance (figure).”

WOW, impressive.
 

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Will the A8 be available now when ordering, or coming out later.
 

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The A8 is available, and there are some 2015's that are built waiting on QC. My 2015 A8 is still waiting on DSOM paint, but the order shows my A8 tranny.
 

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To my knowledge all 2015s will include the A8
 
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More info/details from Media.GM.


Media.GM said:
New 8-Speed Enables Quicker, More Efficient Corvette: GM-designed, patented paddle-shift gearbox rivals dual-clutch performance!

The all-new, GM-developed Hydra-Matic 8L90 paddle-shift eight-speed automatic transmission offered in the 2015 Corvette Stingray and Z06 enhances performance and efficiency, while delivering exceptional refinement and world-class shift responsiveness that rivals the world’s best dual-clutch transmissions.

In fact, in the 2015 Corvette Stingray, it enables a class-leading 29-mpg EPA highway estimate – a 3.5-percent increase in fuel economy over the previous six-speed automatic – and a quicker 0-60 time of 3.7 seconds, all while delivering wide-open-throttle upshifts quicker than those of the dual-clutch transmission offered in the Porsche 911.

“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. “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.”

With four simple gearsets for optimal efficiency and five clutches (two brake clutches and three rotating clutches), creative packaging enables the new eight-speed automatic to fit the same space as the previous six-speed automatic – and the powerflow only uses two open clutches for low spin losses, which enhances efficiency. Extensive use of aluminum and magnesium also make it more than eight pounds (4 kg) lighter than the six-speed.

The greater overall performance and efficiency enabled by the 8L90 in the Corvette is due primarily to a new, wider 7.0 overall gear ratio spread, which enhances off-the-line performance with a more aggressive first gear ratio – 4.56 vs. 4.03 on the six-speed – helping achieve the quicker 0-60 time.

The top gear ratio is 0.65 vs. the six-speed’s 0.67. 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. The lower engine speed reduces fuel consumption, while a new torque converter design enhances refinement, particularly during low-speed gear changes.

Stingray models equipped with the Z51 Performance Package feature a more aggressive 2.73 axle ratio, while the Corvette Z06 features the 2.41 axle ratio.

Ratios compared: eight-speed automatic vs. six-speed automatic


2015 Corvette Stingray / Z06
2014 Corvette Stingray
Type:
8L90 eight-speed
paddle-shift automatic
6L80 six-speed
paddle-shift automatic
Gear ratios :)1)


First:
4.56
4.03
Second:
2.97
2.36
Third:
2.08
1.53
Fourth:
1.69
1.15
Fifth:
1.27
0.85
Sixth:
1.00
0.67
Seventh:
0.85
N/A
Eighth
0.65
N/A
Reverse:
3.82
3.06
Axle ratio:
2.41 (Stingray / Z06)
2.73 (Stingray with Z51)
2.56 (std.)
2.73 (with Z51)


World-class performance
Designed and built by GM, the paddle-shift 8L90 transmission delivers world-class shift times that rival the best dual-clutch designs.

“The Corvette’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 Kaveh. “It was designed to enhance the driving experience, with performance on par with dual-clutch designs, but without sacrificing refinement.”

For performance driving, the transmission offers full manual control via steering wheel paddles. A new transmission-controls system and unique algorithms deliver shift performance that rivals the dual-clutch/semi-automatic transmissions found in many supercars – but with the smoothness and refinement that comes with a conventional automatic fitted with a torque converter.

In fact, a new, Gen II transmission controller 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.

Smaller steps between gears, compared to the previous six-speed automatic (see chart above), keep the engine within the sweet spot of the rpm band, making the most of its horsepower and torque to optimize performance and efficiency. Additionally, a torque converter design with a turbine damper complements performance with excellent refinement at low engine speeds.

Unique clutch and torque converter specifications matched to the torque capacity of the Stingray’s LT1 6.2L naturally aspirated engine and the Z06’s LT4 supercharged engine distinguish the applications for the different Corvette models.

Architectural and design features
More than 550 computer-aided engineering analysis were made during the development of the 8L90 to ensure strength, durability, performance and refinement. The architecture features a one-piece case with an integral bell housing for enhanced powertrain stiffness, as well as a detachable extension for the Corvette’s rear transaxle arrangement.

Similar to GM’s six-speed automatic design, the eight-speed’s architecture locates the grounding clutches rearward of the middle of the structure, outside the gearsets. However, the grounding clutches are splined to the case, eliminating the center support, which reduces weight.

This architecture also features a turbine shaft node that reaches to the outside of the barrel, enabling easy execution of a high-resolution magnetic speed sensor. The turbine shaft itself is very short, keeping oil channel drill lengths to a minimum. The rotating clutches are located near the front of the transmission, with short oil feed channels, supporting the transmission’s very fast shifts.

Additional design and performance features include:

Clutch compensators are fed by lubrication oil rather than the dedicated and regulated feed design of the 6L80. There are two benefits of this new design feature: The reduction of one oil channel between the valve body and the rotating clutches, which reduces the number of rotating oil seals and oil channels within the turbine shaft; and, secondly, the capability for rapid discharge of oil in the compensators during clutch apply, for greater control.

An industry-first off-axis, chain-driven binary vane-type pump – located within the valve body – effectively allows for two pumps in the packaging size of a single, which contributes to lower parasitic losses and optimal priming capability, as well as ideal oil routing to the controls system.

The binary pump enables a 60-percent reduction in pump torque at points that represent large portions of the operating duty cycle, compared to the 6L80 six-speed, which is a significant contributor to the overall efficiency gains offered by the 8L90.
The binary pump is located very low in the sump, for greater cold prime operation – as low as -40 F (-40 C) and excellent high-speed operation with stable line pressure.

Thanks to a new torque converter clutch friction lining and a new control strategy, the 8L90’s squashed torque converter uses conventional dual-path converter feeds.

New synthetic fluid with improved cold temperature performance and reduced friction characteristics.

Shift time quickness and improved responsiveness are accomplished with the new Gen II controls system. VFS solenoid technology and three internal speed sensors give the 8L90 the capability for world-class shift performance. The new transmission controller is mounted external to the transmission and has a processor that executes hundreds of calculations and commands every 6.25 milliseconds.

The 8L90 is built at GM’s Toledo, Ohio, transmission facility.
New 8-Speed Enables Quicker, More Efficient Corvette
 

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It's curious that they only compared 1st to 2nd, 2nd to 3rd and downshift from 60 mph shift speeds to the PDK.
The argument could be made that even comparing it so favorably to the Porsche Doppelkupplung is a victory in itself. The PDK, especially the "Sport" version found in the GT3 and TT's, is a fantastic gearbox with virtually no peer.
S.
 

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To my knowledge all 2015s will include the A8
So you are saying they are doing away with the M7 for 2015? Where did you read that?
 

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All StingRay's and all Z06's will offer all the option of the 7-speed manual OR the 8-speed automatic trans.

The comment above "that all 2015's would be automatics" was not inaccurate, but responding to whether one could still get a 6-speed auto -- and that answer is no, for that auto trans is now Corvette past history.
 

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So you are saying they are doing away with the M7 for 2015? Where did you read that?
No, what he is saying is that the only automatic available is the A8. No more A6. M7 is still the base transmission.
 

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So you are saying they are doing away with the M7 for 2015? Where did you read that?
I think he means all automatic tranny's will be the 8 speed.
 
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EDITED !

One thing was just putting me in the trouble: GM has always communicated about the gear changes speed AT WOT but on the track or on the road we are waiting for a very quick reactivity all the time and not only at WOT !! This car have so much torque that there is no need to be constantly at full throttle to use it in the best way, so for me this commercial argument is not the reflect of a real advantage.

It seems that the choice would have to be done regarding what you are expecting to do with your Vette. My choice is done now.
 

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Discussion Starter · #15 ·
2015 Corvette Stingray eight speed automatic First drive | Autoweek

”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."
 

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This first report is just confirming what some of us were thinking about what could be the A8 : an excellent road transmission, in any case better than the A6, but still not at the same level than a Porsche PDK one in track use.
One more time the double clutch would have been a better choice for the road AND the track using.

One thing was just putting me in the trouble: GM has always communicated about the gear changes speed AT WOT but on the track or on the road we are waiting for a very quick reactivity all the time and not only at WOT !! This car have so much torque that there is no need to be constantly at full throttle to use it in the best way, so for me this commercial argument is not the reflect of a real advantage.

It seems that the choice would have to be done regarding what you are expecting to do with your Vette. My choice is done now.
There is no reason not to be upshifting at WOT on-track.
And DCT's are laggy in upshifts at part throttle, the PDK less so than other DCT's, but shift speed at part throttle is still slower than at WOT. The PDK is the current benchmark, so the A8 comparing so well is a victory in its first year of production.
There is a very real possibility that the A8 will turn out to be a better trans than many other DCT's, including the GR6 in the GT-R. The issue IMO is whether or not GM has solved the cooling issue (the GT-R has a similar cooling issue on-track).
S.
 

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Sorry, I was reading this thread on my iPhone and I was zapping a part of the first post !
You're right, it seems that the first comment is better than expected for the track use, on the other side, we just have to wait for a such use during a hot day and as I plan to use my C7 on the track as often as with my other cars, the transmission choice have to be carefully done.

As said before I have nothing against the A8 but I feel that I will not have a reply to all my questions before to choose between the 2 gearboxes, but over here we have a privilege : we still don't know the 2015 prices !... so perhaps some new test will be available until my choices deadline.

I have seen the video of this test driving (second link of the first post) but the car was quite always going from 2nd to 3rd gear with one time for 3 seconds up to 4th gear. Max speed was 97mph but more commonly 70-80 and it was under very cloudy weather. The gear change sound is between an automatic and a manual one.
Hope to see a test on a big and high speed track.
 

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I don't know about the Porsche, but I have a VW with a six speed dual clutch transmission, and the fluid in it has to be changed every 40K miles.
 

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2015 Corvette Stingray eight speed automatic First drive | Autoweek

”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."
IS THIS GREAT OR WHAT! No question GM has the ability to make this transmission a home-run...and it's looking like they did just that! The way the transmission behaves on the road course is simply amazing.
 

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Another comment, with much nuances, from another Website:

Needless to say the new eight-speed automatic works at the track, but this should come with a caveat – don’t touch the paddles. The software engineering has been so well sorted out that the computer is calling for gears in advance to the driver actually needing them, so when the change occurs it’s at the exact right moment. Since this is a “regular” automatic, using the paddle shifters to “manually” select a gear is followed by a lengthy delay.

It’s the one thing a conventional automatic cannot match compared to a dual clutch transmission (DCT), the response time from a driver’s input to the physical gear change. Sure the new eight-speed can change gears lightning quick, but a DCT has already pre-loaded the next gear and can react to a new input much faster. I will say that response time does feel quicker from the Corvette’s eight-speed automatic than the eight-speed autos I’ve recently sampled, including in the Jaguar F-Type.

2015 Chevy Corvette Stingray Review: Car Reviews

It's surprising to read that the paddles use makes the shifting slower.
 
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