BluegrassMotorsport

Bingo.

Nothing else should matter. If the C7 performs the way a Corvette rightfully should, does the transmission really matter? There are a few automatic boxes on the market today that are said to shift nearly or as well as a DCT box.

BeaZt

If you want to have fun get a manual, if you want to go fast get an automatic

235265283...

Several months ago, on another CF C7 speculation thread, I posted my prediction (guess, actually) that the 2014 C7 would not have a DCT option. In a nutshell, my reasoning was based on GM development and manufacturing costs and the fact that, due primarily to Corvette's transaxle and secondarily to its torque, a Corvette DCT couldn't share much with other GM platforms.

With respect to DCT vs. ATs with torque converters, there are substantial differences of course. I think most folks consider a DCT to be superior for "performance" car applications, and it also enables slightly better fuel economy. A torque converter almost always includes a fluid coupling, which gave rise to the negative-implication term "slush box" many years ago. But obviously the A6 (and A8?) have come along way since their 1950s Powerglide and Dynaflow ancestors. But the basic principle of the torque converter has changed little.

So, IMHO, a DCT vs. A6 or A8 difference that is more significant than the crispness of the shifts is: Do you want to disengage the engine from the transmission with automatic clutches or a torque convertor? I think the torque convertor is slightly more "lossy", but its controls can be more passive than those needed for a DCT (more like "fly by wire").

Even though my acquaintances with DCTs love them, I'm pleased with my 2012 C6 A6, and probably wouldn't have paid more for a DCT option if it had been available.

Racer X

You do know that the torque convertor locks up at a certain point (dictated by programing), right? So it is only in the torque path in certain low speed circumstances.

Larry/car

I will always get the manual trans. I enjoy deciding what gear needs selected and it doesn't matter if an automatic will out perform a manual by a fraction of a second. I don't need launch control either. I would rather do it my self.

JoesC5

One of the drawbacks of an auto vs a manual is the extra 125 pounds of dead weight the auto is always carring around. GM spends millions getting 136 pounds removed from the frame,and the buyer adds it back with the auto.

235265283...

Good point. Do you know or are you able to estimate the approximate lockup programming of the current Corvette A6? I can't detect lockup or unlock while driving.

Also: The fact that old (but highly modified) 2-speed Powerglides are the most popular AT used in drag racing cars always perplexed me. Do you know why this is. Do these have torque converter lockup?

235265283...

Good point.

AFVETTE

Then you guys must hate the ancient OHV engines in the vette and wionder how you can own and drive such outdated technology.

The "I'm not gonna buy a C7 because the auto transmission isn't a DCT and keep your C6" is a riot.

Enjoy your C6's, I'm looking forward to the next vette.

not08crmanymore

GM having changed the algorithm in the 2012 Auto Vette might carry over to the c7.DCT's are weird anyway. REAL MANUAL all the way baby!!!

Carver Electrics

Racer X

A torque converter multiplies torque. That is why they are quicker off the line. Automatics don't miss shifts, they have torque multiplcation off the line (kind of like an extra gear that gradually moves to actual gear ratio. So 1st gear is 2.2 to 1. The turque converter may have a 2 to 1 multiplication. SO 1st gear really starts out at about 4.4 to 1 the moves up to 2.2 to 1 then it shift to 2nd which gear at 1 to 1 in a powerglide, but the torque coverter comes into play an makes about 2 to 1 that gradually moves up to 1 to 1.

It is really more complicated than that.

I don't know the lock-up speeds of modern transmissions. I think it varies based on gear, throttle setting, and speed. Maybe other factors as well.

wishihad1-2

I'm glad to see I'm not the only one who has wondered about DCT vs traditional autos. I'm not convinced that DCTs are better when it comes to autos.

First, I would like to point out that a DCT and an F1 gearbox don't have much in common. The F1 boxes are more like motorcycle boxes and they don't bother with clutches once rolling, much less two clutches.

I've often asked people who are sure that DCTs are better what makes them better. Rarely have I gotten a good answer. I think many people have an impression of how a traditional auto works based on years of driving traditional 4 speed autos. With a 4 speed you have larger jumps between gears and probably run longer before locking the TC. I haven't found a good explanation why a DCT should be better than a good modern auto.

Anyway, here are the differences I can think of.
1. A DCT is really disengaged when you are at a light. I would like think because one of the things I hate most about traditional autos is having to hold the brake against the car creeping forward. The down side to the DCT is that, unlike a traditional auto you can't use the transmission to hold the car from creeping forward. I've heard a few people talk about the VW transmissions making noises (just the noise of shifting) when creeping in traffic. If you are truly in stop and go the DCT isn't as nice as the TC. But if you are worried about mileage in stop and go traffic the DCT might do better since you don't have TC drag.

2. Shifting speed. This is one that DCTs really like because they are much faster than traditional manuals. OK. They aren't faster than automatics which as others mentioned never disengage power. The traditional autos have LOTS of clutches. Can we call them Octoclutch-transmissions?

3. Smoothness. I don't think you can beat a modern TC auto for smoothness.

4. That "slushy feeling". I really never liked that disconnected from the engine feel you get with many autos. However, I think with lock up TCs that can largely be eliminated. Still, it is by default not part of a DCT.

Anyway, those are the areas that come to mind and none have me thinking the DCT is significantly better except for mileage when stopped because there is not TC drag.

zland

Regarding DCT, maybe GM knows the market better then some of our wishes & it comes down to added cost of the car? Another consideration is durability & repair costs compared to normal auto trans. Tell me guys, what is the durability & repair costs for a DCT & if it is extreme, my bet is most of you would end up hating it once you paid for it & had to live with it. I feel that way with Ceramic brakes. I would pay extra not to have them, even if I owned a Z06 instead of a base C6.

To put things in perspective, I once wrote an article for the crew chief of a 350Z grand am cars. He stated for him, 1/10th a second lap time difference = success or failure. How many of us really need to be 1/10th of a second faster? For me, it is not the actual 0-60 time or the lap time but the perception of speed & joy of driving it be it on the track or street. My profession is not a professional race car driver nor is my C6 a race car.

JWell

After reading this I figured GM had no interest in a DCT. I would expect that the new transmission will shift as fast or faster than a DCT when the paddles are used but it will remain a torque converter style.
http://www.vetteweb.com/tech/vemp_12...lickety_shift/

Racer X

Interesting. The article has evidence of a new auto being in the C& Corvtte. It seems a lock that it will get the 8 speed auto. Rutta Kunge posted a number of patent applications by GM for 8 speed planetary transmissions. They don't have to be electro-hydraulically shifted automatics, but how they are in most passenger cars. They are also used in ProStock classes in drag racing. They are manually shifted or air shift. Shift times really matter there.


Here is the confirmation of a new transmission for the C7. "But since the invention is not 6L80-specific, it's likely to be included in the transmissions installed in future Corvettes.". This was stated by Gabe Gibson, lead clutch-control calibration engineer for Corvette transmissions and the system's co-inventor.


Very interesting.

BlueOx

I would go for a DCT in my next Vette...my 'clutch' knee is having real problems.

hig4s

Very cool, And while I prefer manuals, I did like the 2011 auto I test drove and if couldn't have found a manual in the color I wanted could have lived with a 2011 A6. And apparently they are even better now.

meadowz06

Folks,
It's no big deal. The Lamborghini Aventador does not have a DCT and it shifts in 50 MILLISECONDS! The auto will be great.

Rapid Fred

Automatic transmissions must be evolving at an exponential pace. I drove, of all things, a new Skyactiv Mazda 3 this weekend. The 6-speed automatic tranny on that thing is amazing, on a $19K car! It is nothing like the "slushboxes" I have known, hated and occasionally have been forced to rent over the years. Apparently, they figured out how to make it respond very quickly, and to keep it in "locked" mode almost all the time. Conversely, even as recently as 2010, the 6-speed automatic GS I test drove felt disappointingly slow and sloppy, just not like a sports car to me. That's why, until this weekend, I would have been very disappointed to see Chevy not stepping up to the DCT plate for the C7. Now, I am convinced they do not need to.

I have owned nothing but stick shift cars for the past 30 years. Nonetheless, put an automatic tranny with manual paddles on a Vette, that responds as quickly, smoothly and crisply as the Skyactive tranny, and I would be OK with it. For the money Chevy is charging, I am sure they can (and will) do as well or better on the C7...