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Old 02-13-2013, 11:26 PM   #1
AtomicZ_Eric
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Default Why manual trans. gets 7th gear, but not auto???

Everyone knows by now that the Stingray's manual trans. will receive a 7th gear, and the A6 will remain @ 6 for this full model change. In the March 2013 issue of Car and Driver Tadge Juechter (Corvette Chief engineer) was asked whether a dual-clutch auto was considered on pages 38-40.

His response edited for brevity:
The number of speeds isn't everything. We introduced the C6 with four-speed automatic, introduced 6 speed in the second year and had a h3ll of a time beating the four speed in both fuel economy & performance. We operate at high torque / high efficiency across a broad RPM range so we don't need more gears.

If that is the case then why add a 7th gear to the MT??? Maybe an engine / trans guy can chime in here. I frequently skip 5th gear in my cars with 6 speeds. I'm failing to see the benefit of 7 gears in this application. Maybe cool with flappy paddles - more accurately a DCT, or single clutch auto - but that seems like a lot of shifting (or skip shifting) with the MT.

Using more gears in smaller displacement / high revving engines to keep the engine in a narrower torque curve is common among Japanese, Italian, etc. automakers. But the logic for Stingray seems odd.

Wanna chime in here Mr. Juechter???
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Old 02-13-2013, 11:28 PM   #2
Gary '09 C6
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...and isn't the future (MY 2016 ?) C7 automatic supposed to have 8 speeds ?
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Old 02-14-2013, 12:01 AM   #3
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Quote:
Originally Posted by Gary '09 C6 View Post
...and isn't the future (MY 2016 ?) C7 automatic supposed to have 8 speeds ?
I believe Aisin 8 speed rumors have been prevalent prior to the debut. Even if the rumors are correct I'm failing to understand the Chief's logic with MT7 vs. A6... or A8 for that matter. What ROI (return on investment) do they receive for this change? Maybe an engineering accountant can chime in now...

Mr. Juechter, Moss, Bailey.... I'm not trying to be picky (although it certainly seems like it). I'm just trying to understand, from an engineering standpoint, the operation of one system compared to another. Again, I frequently skip shift on my 6 speeds, so I'm not sure where a 7th becomes useful? Does it have something to do with cylinder deactivation?

Again, I'm not knocking the transmissions - just trying to gain some understanding.
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Old 02-14-2013, 12:20 AM   #4
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It's my understanding that 1st-6th gears are pretty close to the C6 gears, and 7th is another, slightly taller, overdrive. It's meant strictly for highway cruising to eek out just a touch more MPG.
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Old 02-14-2013, 01:03 AM   #5
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Sooner or later they will have to upgrade the auto to 7 or 8 gears. He also said the they did not find a dual clutch that could handle the C7 torque, but i don't buy that because the 911 Turbo and the Ferrari Berniletta both have more torque the C7 and they used the dual clutch trans.
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Old 02-14-2013, 01:27 AM   #6
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I think it comes down to they could quickly & cheaply upgrade to a 7 speed manual vs the Auto in which will take a lot more engineering to get it done.
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Old 02-14-2013, 07:48 AM   #7
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Originally Posted by ivanjo11 View Post
Sooner or later they will have to upgrade the auto to 7 or 8 gears. He also said the they did not find a dual clutch that could handle the C7 torque, but i don't buy that because the 911 Turbo and the Ferrari Berniletta both have more torque the C7 and they used the dual clutch trans.
Do they have to up the number of gears in the A6??? If there's little or no performance benefit then why upgrade? Maybe continual refinement is ok... It seems to work for the 911.

I agree that there are transmissions that can handle the torque, but they continue to say indicate fitment may be an issue. Maybe the Vette's rear end is more cramped than some others. Please correct me if I'm wrong but I believe the clutch is at the rear of the car with the trans. Maybe other auto makes with front engine/rear transmissions have the clutch up front? That one I'm definitely clueless about.

As an engineer I'm skeptical of "change for the sake of change." Maybe the 7th gear let them squeeke past gas guzzler tax? What's the real reason for the switch?!

I'm anxious to drive one and see how it feels to row through 7 speeds... Or maybe ship shift two lol.
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Old 02-14-2013, 08:13 AM   #8
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I believe that the gears in the 7 speed are geared different than the currant 6 speed, in the C6 5th gear is where you reach top speed and 6th is overdrive. In the C7, 4th gear is 1 to 1 and you will reach top speed there, 5,6,7 are overdrives. So now you are driving a techie 4 speed, your skip shift here will more than not be 2nd to 4th, and I bet it comes set up that way, also guessing that when in sport or track mode that is killed
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Old 02-14-2013, 08:30 AM   #9
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Quote:
Originally Posted by rcooper View Post
I believe that the gears in the 7 speed are geared different than the currant 6 speed, in the C6 5th gear is where you reach top speed and 6th is overdrive. In the C7, 4th gear is 1 to 1 and you will reach top speed there, 5,6,7 are overdrives. So now you are driving a techie 4 speed, your skip shift here will more than not be 2nd to 4th, and I bet it comes set up that way, also guessing that when in sport or track mode that is killed
The C6 is also 1-1 in 4th gear making 5th and 6th overdrives. Top speed in the C7 should be in either 5th or 6th depending on final ratio numbers.
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Old 02-14-2013, 09:26 AM   #10
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Quote:
Originally Posted by AtomicZ_Eric View Post
Do they have to up the number of gears in the A6??? If there's little or no performance benefit then why upgrade? Maybe continual refinement is ok... It seems to work for the 911.

I agree that there are transmissions that can handle the torque, but they continue to say indicate fitment may be an issue. Maybe the Vette's rear end is more cramped than some others. Please correct me if I'm wrong but I believe the clutch is at the rear of the car with the trans. Maybe other auto makes with front engine/rear transmissions have the clutch up front? That one I'm definitely clueless about.

As an engineer I'm skeptical of "change for the sake of change." Maybe the 7th gear let them squeeke past gas guzzler tax? What's the real reason for the switch?!

I'm anxious to drive one and see how it feels to row through 7 speeds... Or maybe ship shift two lol.
Some of these 'messages to Tadge' would be far more effective as actual messages YOU SEND TO TADGE vs putting it here on CF thinking he comes here to get his email.

Also, I'm sure that 'as an engineer' you know that everything you do in the course of your daily work doesn't require you to explain it to the consumer on a public forum. BTW, engineers are often called upon to fulfill 'change for the sake of change' at the whim of marketing/upper management.

I'm sure part of it is economics. Does it make economic sense to force faster development of a 7 spd auto that you don't really need but that the marketing folks are screaming for? They already have the 7 spd manual and are working with Ford on 10 spd (essentially like a CVT, which would be very interesting) autos for performance vehicles.
http://www.autoblog.com/2012/10/01/f...eed-gearboxes/

Last edited by BlueOx; 02-14-2013 at 09:33 AM.
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Old 02-14-2013, 09:35 AM   #11
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Right now, I think its all about trying to eek out every little bit of fuel economy. By trying ot keep rpm's lower in every gear for "normal driving" it helps with the enrgy modeling and overall ratings. By doing this, it helps smooth out the overall corporate mpg rating, which is necessary to meet federal standards? most of wont drive our vettes in this manner though. sometimes its about meeting some performance mandate, other times simply marketing right? they could probably build a two speed powerglide trans and call it a day, but it wouldnt do everything we want it to do for the car.

I just bought a new 13 pickup for the business, and it has a six speed auto that keeps the motor pulling less than 1200 rpm through the range, unless you mash the throttle. it does very well on fuel economy as compared to my 2011 platinum with a four speed.
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Old 02-14-2013, 09:39 AM   #12
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Quote:
Originally Posted by Gary '09 C6 View Post
...and isn't the future (MY 2016 ?) C7 automatic supposed to have 8 speeds ?
I think Tadge stated there was nothing available that would fit the C7, basically no direct bolt in transmission. Therefore, they are developing a in house 8 speed Hydra-Matic. In his statement he was evasive on the precise date or even if it was a 8 speed auto, but that could have been for the sake of selling the A6 before the A8 comes out in a year or two. Major manufacturers are going with 8 speed autos, Dodge has had a 8 speed available and has stated they are looking at a 10 to 12 speed for the future.
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Old 02-14-2013, 09:44 AM   #13
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Quote:
Originally Posted by AtomicZ_Eric View Post
Wanna chime in here Mr. Juechter???
He probably won't because he doesn't surf Corvette Forum. Neither do many of his minions.

The days of manual transmissions being significantly more fuel-efficient than automatics is basically over. With the computers at play, an automatic-equipped car and bumble down the road and hit an acceptable (whatever that number is) FE number. Manuals are trickier from an engineering perspective because of that squishy thing (driver) making the gear decisions.

That may be part of it.

Further, GM's pretty keen on using their own internally developed automatic tranmissions. For the Corvette, they don't even bother making a manual; they leave that up to the folks at TREMEC. It's quite possible that GM has a 7-speed auto in the works, and TREMEC was able to get the 7-speed manual out faster. That one's purely a guess though.

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Old 02-14-2013, 09:46 AM   #14
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Quote:
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I think Tadge stated there was nothing available that would fit the C7, basically no direct bolt in transmission.
Well C7 is a new car no surprise that there are not many bolt-on automatics This just says that automatic is more of a afterthought and C7 was not developed high performance automatic in mind.(And of course they promote now hell out of the M7)
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Old 02-14-2013, 09:53 AM   #15
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Need more coffee ...........
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Old 02-14-2013, 10:09 AM   #16
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Why doesn't the auto get a 7 or 8 speed? B/c this is GM. They are always behind. There is a reason they are in the red.
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Old 02-14-2013, 10:14 AM   #17
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Originally Posted by Never-Enough View Post
Why doesn't the auto get a 7 or 8 speed? B/c this is GM. They are always behind. There is a reason they are in the red.
GM was profitable in 2012 to the tune of approximately $5 billion.

http://www.forbes.com/sites/joannmul...ut-to-explode/

http://www.usatoday.com/story/money/...arter/1918293/

Last edited by dmporter31; 02-14-2013 at 10:18 AM.
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Old 02-14-2013, 10:25 AM   #18
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Net?
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Old 02-14-2013, 10:38 AM   #19
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The A6 already has a great gear ratio spread than the M6. It goes from 4.02 to .67 with a 2.56 rear gear so 10.29 to 1.72 final drive. The 6 speed goes from 2.66 to .5 or 2.97 to .57 with a read gear of 3.42 so 9.1 to 1.71 or 10.16 to 1.95 final ratios. So the spread for the A6 is 6 and the spread for the M6 is 5.2 or 5.3. The M7 spread is 6.33 or 6.19 and final drive ratios are 9.1 to 1.44 or 10.16 to 1.64. This brings it more in line with the A6. The spread is slighty smaller for the A6 but, not really because the torque convertor acts as a gear multiplier, so the effective spread is actually higher.

So the Manual got more gears because fuel milage was improved more on it.
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Old 02-14-2013, 11:09 AM   #20
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Quote:
Originally Posted by DCBE View Post
I think Tadge stated there was nothing available that would fit the C7, basically no direct bolt in transmission. Therefore, they are developing a in house 8 speed Hydra-Matic. In his statement he was evasive on the precise date or even if it was a 8 speed auto, but that could have been for the sake of selling the A6 before the A8 comes out in a year or two. Major manufacturers are going with 8 speed autos, Dodge has had a 8 speed available and has stated they are looking at a 10 to 12 speed for the future.
I read the same - nothing existing fits the architecture of the C7
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