Will the ME have a DCT
12-11-2017, 12:24 PM
#121
Last edited by SSsedanM6; 12-11-2017 at 12:28 PM.
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Senna1994 (12-14-2017)
12-13-2017, 04:05 PM
#122
Drifting
I have test driven Mercedes renntech SL63 previous planetary computer controlled transmission without a torque converter and it was pretty good. I think we might be pleased with that type of transmission in the c8
Maybe GM will go that route for the c8. I believe it was a better driving experience than the previous torque converter AMG model..
Will the GM planetary gearboxes in a corvette c8 need a torque converter? That might be a unique direction for the c8
Planetaries are nice from a ratio standpoint; In a non-planetary, first gear doesn't have as much gear tooth contact area and the high stresses can limit the ratio; a planetary typically has more contact area and can handle more torque. If they decide to use a DCT for the C8, it would be nice to be able to match the ratio spread on the A8, at least, and not go with something like the Tremec 9007 which is basically a 4-speed transmission with several overdrives.
People already complain about the ratio drop on the 4-5 shift on the A8 ..... take a look at the Tremec for comparison.
I don't see many off-the-shelf DCTs that look like good performance replacements for the A8 in terms of torque load and ratio spread, and the cost to develop a brand new DCT could easily exceed Corvettes entire budget. GM is also known for spreading costs out across multiple platforms...... In the end, cost will more than likely dictate what we wind up with.
Last edited by RedLS6; 12-13-2017 at 04:08 PM.
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JerriVette (12-17-2017),
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12-14-2017, 09:50 AM
#123
Team Owner
In the C7, GM relied on the ability of the torque converter to dampen active fuel management driveline harmonics in the A8 cars, which allowed them to more aggressively activate AFM on the A8 cars. I believe Tadge referred to this as one of the enablers for the AFM system to provide a fuel economy boost for the A8 cars through more aggressive activation. I'm hoping that they can totally eliminate AFM from the C8, but this may be another variable in the equation relating transmission type to cylinder deactivation to fuel economy. The clutched planetary in the Mercedes looks interesting.
Planetaries are nice from a ratio standpoint; In a non-planetary, first gear doesn't have as much gear tooth contact area and the high stresses can limit the ratio; a planetary typically has more contact area and can handle more torque. If they decide to use a DCT for the C8, it would be nice to be able to match the ratio spread on the A8, at least, and not go with something like the Tremec 9007 which is basically a 4-speed transmission with several overdrives.
People already complain about the ratio drop on the 4-5 shift on the A8 ..... take a look at the Tremec for comparison.
I don't see many off-the-shelf DCTs that look like good performance replacements for the A8 in terms of torque load and ratio spread, and the cost to develop a brand new DCT could easily exceed Corvettes entire budget. GM is also known for spreading costs out across multiple platforms...... In the end, cost will more than likely dictate what we wind up with.
Planetaries are nice from a ratio standpoint; In a non-planetary, first gear doesn't have as much gear tooth contact area and the high stresses can limit the ratio; a planetary typically has more contact area and can handle more torque. If they decide to use a DCT for the C8, it would be nice to be able to match the ratio spread on the A8, at least, and not go with something like the Tremec 9007 which is basically a 4-speed transmission with several overdrives.
People already complain about the ratio drop on the 4-5 shift on the A8 ..... take a look at the Tremec for comparison.
I don't see many off-the-shelf DCTs that look like good performance replacements for the A8 in terms of torque load and ratio spread, and the cost to develop a brand new DCT could easily exceed Corvettes entire budget. GM is also known for spreading costs out across multiple platforms...... In the end, cost will more than likely dictate what we wind up with.
The TR-7007 has an input torque of 516 Lb-ft and has 4 underdrive gears, 1 direct drive gear and 2 overdrive gears. 516 lb-ft will be sufficient for most applications(plenty to handle a 470 lb-ft LT1, or another 6.2L version with around 550 HP and 516 lb-ft.
The TR-9007 has an input torque of 664 lb-ft and has 4 underdrive gears and 3 overdrive gears. 664 lb-ft will be sufficient of most applications of 4.2l and 5.5LV8's with twin turbos. For example, the Porsche Gt2 RS has a 3.8L b6 with 700 HP and 553 lb-ft, the Ford GT has a 3.5L V6 with 647 HP and 550 lb-ft, the AMG GT R has a 4L V8 with 557 HP and 516 lb-ft, and the McLaren Senna has 789 HP and 590 lb-ft. The Tremec TR-9007 will handle the torque of all those high performance cars, so it should be able to easily handle a 4.2L or a 5.5L mid engine Corvette.
What is impressive with the two Tremec DCT's is that they both have better gear ratios than the current TR-6070 and nearly equal to the M5U A8.
Last edited by JoesC5; 12-14-2017 at 11:20 AM.
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Senna1994 (12-14-2017)
12-14-2017, 03:14 PM
#125
Drifting
Tremec has two DCT's.
The TR-7007 has an input torque of 516 Lb-ft and has 4 underdrive gears, 1 direct drive gear and 2 overdrive gears. 516 lb-ft will be sufficient for most applications(plenty to handle a 470 lb-ft LT1, or another 6.2L version with around 550 HP and 516 lb-ft.
The TR-9007 has an input torque of 664 lb-ft and has 4 underdrive gears and 3 overdrive gears. 664 lb-ft will be sufficient of most applications of 4.2l and 5.5LV8's with twin turbos. For example, the Porsche Gt2 RS has a 3.8L b6 with 700 HP and 553 lb-ft, the Ford GT has a 3.5L V6 with 647 HP and 550 lb-ft, the AMG GT R has a 4L V8 with 557 HP and 516 lb-ft, and the McLaren Senna has 789 HP and 590 lb-ft. The Tremec TR-9007 will handle the torque of all those high performance cars, so it should be able to easily handle a 4.2L or a 5.5L mid engine Corvette.
What is impressive with the two Tremec DCT's is that they both have better gear ratios than the current TR-6070 and nearly equal to the M5U A8.
The TR-7007 has an input torque of 516 Lb-ft and has 4 underdrive gears, 1 direct drive gear and 2 overdrive gears. 516 lb-ft will be sufficient for most applications(plenty to handle a 470 lb-ft LT1, or another 6.2L version with around 550 HP and 516 lb-ft.
The TR-9007 has an input torque of 664 lb-ft and has 4 underdrive gears and 3 overdrive gears. 664 lb-ft will be sufficient of most applications of 4.2l and 5.5LV8's with twin turbos. For example, the Porsche Gt2 RS has a 3.8L b6 with 700 HP and 553 lb-ft, the Ford GT has a 3.5L V6 with 647 HP and 550 lb-ft, the AMG GT R has a 4L V8 with 557 HP and 516 lb-ft, and the McLaren Senna has 789 HP and 590 lb-ft. The Tremec TR-9007 will handle the torque of all those high performance cars, so it should be able to easily handle a 4.2L or a 5.5L mid engine Corvette.
What is impressive with the two Tremec DCT's is that they both have better gear ratios than the current TR-6070 and nearly equal to the M5U A8.
Taking a look at the TR-9007, though: it has a 5.61:1 overall ratio (the A8 is 7.01:1). That's an advantage for the A8, given the prior emphasis on manufacturers to try to maintain the engine in a narrow operating region for fuel economy.
The Tremec has a 3.14 first gear, versus 4.56 in the A8. If I were to drop this Tremec into my C7Z (and hire some magic elves to make it work), my car would be a dog off the line compared to the A8. In order to bring back the lower effective ratios, I'd need to replace my 2.41 ring and pinion with a 3.50 gear setup. While this doesn't sound bad, manufacturers usually prefer the lower numerical ratio hypoids because they have lower parasitic losses, and better economy, than the higher ratios.
Corvette really doesn't have a major gear ratio problem with the A8; they don't really have a shifting problem either, as the A8 can shift quickly once the clutch-brake commands are processed; what they seem to have is a transmission control problem, measured in shift delay and feel.
GM could certainly use the TR-9007 behind a high-hp high-rpm engine if it helped out with the shifting control and feel issues; it might even be a decent solution all things considered, I just wouldn't consider it an optimal replacement for what we have now. However, GM does have a history of making money by giving us non-optimal (but pretty good) stuff at a reasonable price.
Last edited by RedLS6; 12-14-2017 at 03:15 PM.
12-14-2017, 04:10 PM
#126
Race Director
Gallardo single clutch people that mostly don’t like are ones that don’t understand it. It is like driving a manual transmission, you have to let off the gas when shifting. No it is not an automatic! If you rode with me in my car you would get a smooth ride since I know how to drive it.
12-14-2017, 04:43 PM
#127
Team Owner
It's likely that neither Tremec will fit where a transaxle needs to go.
Taking a look at the TR-9007, though: it has a 5.61:1 overall ratio (the A8 is 7.01:1). That's an advantage for the A8, given the prior emphasis on manufacturers to try to maintain the engine in a narrow operating region for fuel economy.
The Tremec has a 3.14 first gear, versus 4.56 in the A8. If I were to drop this Tremec into my C7Z (and hire some magic elves to make it work), my car would be a dog off the line compared to the A8. In order to bring back the lower effective ratios, I'd need to replace my 2.41 ring and pinion with a 3.50 gear setup. While this doesn't sound bad, manufacturers usually prefer the lower numerical ratio hypoids because they have lower parasitic losses, and better economy, than the higher ratios.
Corvette really doesn't have a major gear ratio problem with the A8; they don't really have a shifting problem either, as the A8 can shift quickly once the clutch-brake commands are processed; what they seem to have is a transmission control problem, measured in shift delay and feel.
GM could certainly use the TR-9007 behind a high-hp high-rpm engine if it helped out with the shifting control and feel issues; it might even be a decent solution all things considered, I just wouldn't consider it an optimal replacement for what we have now. However, GM does have a history of making money by giving us non-optimal (but pretty good) stuff at a reasonable price.
Taking a look at the TR-9007, though: it has a 5.61:1 overall ratio (the A8 is 7.01:1). That's an advantage for the A8, given the prior emphasis on manufacturers to try to maintain the engine in a narrow operating region for fuel economy.
The Tremec has a 3.14 first gear, versus 4.56 in the A8. If I were to drop this Tremec into my C7Z (and hire some magic elves to make it work), my car would be a dog off the line compared to the A8. In order to bring back the lower effective ratios, I'd need to replace my 2.41 ring and pinion with a 3.50 gear setup. While this doesn't sound bad, manufacturers usually prefer the lower numerical ratio hypoids because they have lower parasitic losses, and better economy, than the higher ratios.
Corvette really doesn't have a major gear ratio problem with the A8; they don't really have a shifting problem either, as the A8 can shift quickly once the clutch-brake commands are processed; what they seem to have is a transmission control problem, measured in shift delay and feel.
GM could certainly use the TR-9007 behind a high-hp high-rpm engine if it helped out with the shifting control and feel issues; it might even be a decent solution all things considered, I just wouldn't consider it an optimal replacement for what we have now. However, GM does have a history of making money by giving us non-optimal (but pretty good) stuff at a reasonable price.
Compare that with the A8's 4.56:1 1st gear combined with a 2.41:1 rear gear(10.99:1). In addition with the TR-7007 vs the A8, you will have less RPM drop as the gears are tighter together(close ratio).
The TR-7007's 516 lb-ft capacity will handle most applications and the TR-7007 is smaller and lighter than the TR-9007.
But, looking at the CAD's, I kind of doubt that GM is using an out of the box DCT from Tremec. Possible that some of the Tremec's guts are used in a new housing that also includes the differential as an integral part of the transaxle. By the same token, they are not using an out of the box A8 either, or an out of the box manual either.
Any transmission they use will have to be engineered for the mid engine application.
Last edited by JoesC5; 12-14-2017 at 05:25 PM.
12-14-2017, 06:52 PM
#128
Drifting
Again, the TR-7007 has a 5.58 ratio spread .... slightly worse than the 9007 and not close to the A8's 7:1. It does have a numerically higher first gear than the 9007, but it compares very poorly in torque capacity to the 9007 and A8 while not coming close to the A8's first gear. I really don't want to take my C8 to the dragstrip and blow my DCT's internals across the track because the design safety factor was lower than it used to be, instead I'd like to hope that we'll get a very durable transmission in the C8 with some margin for torque, like we have now.
If you take the first gear ratio, multiply by the ratio spread, multiply by the torque rating, and divide by the tranny weight, you'll get a performance metric that is dominated by planetaries. The Mercedes transmission is interesting because it combines the performance of a planetary with the engagement of a wet clutch, no TC. Planetaries, on the other hand, usually lag behind slightly in parasitic losses due to the gear mesh and the added rotating clutches.
Another thing no one has mentioned is integration cost. GM has a ton of time and money spent in integrating the A8 and A10 mechatronic controls to the Control Modules....... both in terms of hardware and software development, in terms of algorithm development, and in terms of testing. There's an associated overhead cost when integrating another vendor's IP into your product.
If GM is using an outsourced transmission for the C8, they'll need to integrate it into the platform ... and since the Tremec units already exist, GM would need to build their integration, both hardware and software, around the outsourced architecture. GM could also have been working with Tremec or another vendor for a period of years to develop a new tranny, in which case the transmission could have been architected to more optimally fit GM's hardware, software, and control algorithm platform, along with fuel economy and performance goals.
If you take the first gear ratio, multiply by the ratio spread, multiply by the torque rating, and divide by the tranny weight, you'll get a performance metric that is dominated by planetaries. The Mercedes transmission is interesting because it combines the performance of a planetary with the engagement of a wet clutch, no TC. Planetaries, on the other hand, usually lag behind slightly in parasitic losses due to the gear mesh and the added rotating clutches.
Another thing no one has mentioned is integration cost. GM has a ton of time and money spent in integrating the A8 and A10 mechatronic controls to the Control Modules....... both in terms of hardware and software development, in terms of algorithm development, and in terms of testing. There's an associated overhead cost when integrating another vendor's IP into your product.
If GM is using an outsourced transmission for the C8, they'll need to integrate it into the platform ... and since the Tremec units already exist, GM would need to build their integration, both hardware and software, around the outsourced architecture. GM could also have been working with Tremec or another vendor for a period of years to develop a new tranny, in which case the transmission could have been architected to more optimally fit GM's hardware, software, and control algorithm platform, along with fuel economy and performance goals.
The Tremec TR-7007 which has a rated input torque of 516 lb-ft has a 3.63:1 first gear. Couple that with the 3.42 rear gear used in the manual transmission and you end up with a total gear ratio of 12.41:1.
Compare that with the A8's 4.56:1 1st gear combined with a 2.41:1 rear gear(10.99:1). In addition with the TR-7007 vs the A8, you will have less RPM drop as the gears are tighter together(close ratio).
The TR-7007's 516 lb-ft capacity will handle most applications and the TR-7007 is smaller and lighter than the TR-9007.
But, looking at the CAD's, I kind of doubt that GM is using an out of the box DCT from Tremec. Possible that some of the Tremec's guts are used in a new housing that also includes the differential as an integral part of the transaxle. By the same token, they are not using an out of the box A8 either, or an out of the box manual either.
Any transmission they use will have to be engineered for the mid engine application.
Compare that with the A8's 4.56:1 1st gear combined with a 2.41:1 rear gear(10.99:1). In addition with the TR-7007 vs the A8, you will have less RPM drop as the gears are tighter together(close ratio).
The TR-7007's 516 lb-ft capacity will handle most applications and the TR-7007 is smaller and lighter than the TR-9007.
But, looking at the CAD's, I kind of doubt that GM is using an out of the box DCT from Tremec. Possible that some of the Tremec's guts are used in a new housing that also includes the differential as an integral part of the transaxle. By the same token, they are not using an out of the box A8 either, or an out of the box manual either.
Any transmission they use will have to be engineered for the mid engine application.
Last edited by RedLS6; 12-14-2017 at 07:07 PM.
12-14-2017, 07:30 PM
#129
I do not get your logic. DCT vs single clutch has nothing to do with smooth operation it only has to do with faster shift time that is it. What DCT and single automated clutch cars have you owned?
Gallardo single clutch people that mostly don’t like are ones that don’t understand it. It is like driving a manual transmission, you have to let off the gas when shifting. No it is not an automatic! If you rode with me in my car you would get a smooth ride since I know how to drive it.
Gallardo single clutch people that mostly don’t like are ones that don’t understand it. It is like driving a manual transmission, you have to let off the gas when shifting. No it is not an automatic! If you rode with me in my car you would get a smooth ride since I know how to drive it.
I owned a Gallardo the transmission sucked. Horrible in auto mode clunky and always searching for the correct gear. From a dead stop there is a horrible delay while clutch engages and the car requires a small roll out prior to full acceleration.
Also Lamborghini states clearly in the owners manual that there is no need to lift of the accelerator while shifting.
Do you somehow lift of the accelerator when it's in auto mode?
Read the customer reviews on the Gallardo you see hundreds of complaints regarding the egear poor shift quality and premature clutch wear.
A properly set up transmission should not require that it's driven any different than a TC trans regardless of single clutch or DCT.
Drive a Ferrari 458 or 488 and you will then agree that the egear is just outdated junk transmission.
Lamborghini knew it had issues that why they recommended you not use performance start mode and knew clutch wear was unacceptable.
Granted it got better as software improved but it in my opinion is the worst transmission I have every owned in a modern vehicle.
Surly not suited for a 200k supercar. I must be one of those dumb drivers as I had to replace the clutch at 9k miles.
I think your biased due to being a Lamborghini owner. I know you stated that you have 50k miles on your car! That's great that you enjoy it seeming as a daily driver. But I also read where you no longer have the front diff. working and have it set up rear wheel only. Seems kinda odd to carry around a 200 front diff and not have it drive as intended.
Did the diff go out or did you just decide that you perffered just rear wheel drive?
Please go drive a PDK or a Ferrari or for that matter a Huracan and you will see that your argument about the egear is a waste of time and you will see how poorly it compares to more modern well sorted DCT
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ByByBMW (12-14-2017)
12-14-2017, 08:28 PM
#130
Team Owner
Again, the TR-7007 has a 5.58 ratio spread .... slightly worse than the 9007 and not close to the A8's 7:1. It does have a numerically higher first gear than the 9007, but it compares very poorly in torque capacity to the 9007 and A8 while not coming close to the A8's first gear. I really don't want to take my C8 to the dragstrip and blow my DCT's internals across the track because the design safety factor was lower than it used to be, instead I'd like to hope that we'll get a very durable transmission in the C8 with some margin for torque, like we have now.
If you take the first gear ratio, multiply by the ratio spread, multiply by the torque rating, and divide by the tranny weight, you'll get a performance metric that is dominated by planetaries. The Mercedes transmission is interesting because it combines the performance of a planetary with the engagement of a wet clutch, no TC. Planetaries, on the other hand, usually lag behind slightly in parasitic losses due to the gear mesh and the added rotating clutches.
Another thing no one has mentioned is integration cost. GM has a ton of time and money spent in integrating the A8 and A10 mechatronic controls to the Control Modules....... both in terms of hardware and software development, in terms of algorithm development, and in terms of testing. There's an associated overhead cost when integrating another vendor's IP into your product.
If GM is using an outsourced transmission for the C8, they'll need to integrate it into the platform ... and since the Tremec units already exist, GM would need to build their integration, both hardware and software, around the outsourced architecture. GM could also have been working with Tremec or another vendor for a period of years to develop a new tranny, in which case the transmission could have been architected to more optimally fit GM's hardware, software, and control algorithm platform, along with fuel economy and performance goals.
If you take the first gear ratio, multiply by the ratio spread, multiply by the torque rating, and divide by the tranny weight, you'll get a performance metric that is dominated by planetaries. The Mercedes transmission is interesting because it combines the performance of a planetary with the engagement of a wet clutch, no TC. Planetaries, on the other hand, usually lag behind slightly in parasitic losses due to the gear mesh and the added rotating clutches.
Another thing no one has mentioned is integration cost. GM has a ton of time and money spent in integrating the A8 and A10 mechatronic controls to the Control Modules....... both in terms of hardware and software development, in terms of algorithm development, and in terms of testing. There's an associated overhead cost when integrating another vendor's IP into your product.
If GM is using an outsourced transmission for the C8, they'll need to integrate it into the platform ... and since the Tremec units already exist, GM would need to build their integration, both hardware and software, around the outsourced architecture. GM could also have been working with Tremec or another vendor for a period of years to develop a new tranny, in which case the transmission could have been architected to more optimally fit GM's hardware, software, and control algorithm platform, along with fuel economy and performance goals.
https://media.mbusa.com/releases/201...specifications
The Mercedes Speed-shift MCT(multi-Clutch Technology) transmission that you mentioned is not used in the high performance AMG GT sports car, and the 9 speed planetary transmission with a torque convertor is widely used in the Mercedes lineup. http://documents.epfl.ch/users/f/fr/...s/A1_Paper.pdf
Also note that the AMG DCT, with it's 3.40:1 first gear and it's 3.69:1 differential gear ratio has a final gear ratio of 12.48:1, bettering the A8's 4.56:1 first gear with it's differential gear of 2.41 :1 which equals 10.99:1 or with a 2.73:1 rear gear which equals 12.45:1.
The Mercedes DCT has a better gearing than the C7's A8.
Last edited by JoesC5; 12-14-2017 at 09:18 PM.
12-14-2017, 11:01 PM
#131
The Mercedes AMG GT, AMG GT S, AMG GT C and the AMG GT R uses a 7 speed DCT and not a planetary transmission with a clutch instead of a torque convertor, in their high performance two seat sports car.
https://media.mbusa.com/releases/201...specifications
The Mercedes Speed-shift MCT(multi-Clutch Technology) transmission that you mentioned is not used in the high performance AMG GT sports car, and the 9 speed planetary transmission with a torque convertor is widely used in the Mercedes lineup. http://documents.epfl.ch/users/f/fr/...s/A1_Paper.pdf
Also note that the AMG DCT, with it's 3.40:1 first gear and it's 3.69:1 differential gear ratio has a final gear ratio of 12.48:1, bettering the A8's 4.56:1 first gear with it's differential gear of 2.41 :1 which equals 10.99:1 or with a 2.73:1 rear gear which equals 12.45:1.
The Mercedes DCT has a better gearing than the C7's A8.
https://media.mbusa.com/releases/201...specifications
The Mercedes Speed-shift MCT(multi-Clutch Technology) transmission that you mentioned is not used in the high performance AMG GT sports car, and the 9 speed planetary transmission with a torque convertor is widely used in the Mercedes lineup. http://documents.epfl.ch/users/f/fr/...s/A1_Paper.pdf
Also note that the AMG DCT, with it's 3.40:1 first gear and it's 3.69:1 differential gear ratio has a final gear ratio of 12.48:1, bettering the A8's 4.56:1 first gear with it's differential gear of 2.41 :1 which equals 10.99:1 or with a 2.73:1 rear gear which equals 12.45:1.
The Mercedes DCT has a better gearing than the C7's A8.
This is simple if GM want to have the C8 high performance model compete with Porsche, Lamborghini, Audi,Ferrari, Maclaren there is no debate.
Car must have a DCT. Period end of story. Drive a Ferrari 458 or 488 or a 911 with PDK. The A8 simple cannot be mentioned in the same breath as these DCT trans.
Porsche sell less than 50k car per year. Ferrari less than 8k per year . Lamborghini less than 8k per year.
They simple charge an extra 4k to 8k and offer a proper DCT.
I own a C7 Callaway SC757 with A8 and also a 2015 458 Italia there is no comparison the Ferrari DCT source from Getrag is night and day better trans. In auto mode is every bit as good as an A8 in manual mode both up shift and down shift are lighting quick. The A8 has horrible lag in manual mode.
So why you all live to show of your intelligence and knowledge of how this transmission work. I say WHO CARES ? GM either uses a DCT or again ask it's customer to settle for an inferior transmission.
With the top of line C8 mid engine is going to be over 150k with option anything less than a DCT just won't do. Period.
For those that say GM won't charge that much I say look at the C7 ZR1 base of 120k add 3 lt 9k now your at 130 with only one option selected.
the top of line mid engine may start at 130k but will easily surpass 150k with options. For that kind of money GM can't expect buyer to settle for an inferior transmission.
They told all us A8 buyer it was as fast as a PDK which was a flat out lye.
It only shift that fast on wide open throttle set in track mode and auto mode.
The manual mode sucks and for a 110k to 120k car their customer deserve better.
plus GM sell 40k Vetts per year also the DCT could be used in the high performance Camero and V series Cadillac to spread the cost around.
Rant over just to me there no debate except from folks that have not driven a well sorted DCT.
Last edited by vetteman41960; 12-15-2017 at 10:17 AM.
12-15-2017, 08:49 AM
#132
Le Mans Master
Member Since: Dec 2004
Location: AZ
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St. Jude Donor '06-'08-'10-'11-'12-'13 '14-'15-'16-'17-'18-'19
It's one of the reasons I don't spend nearly as much time here on CF as I used to.
Thanks for your posts.
Last edited by ByByBMW; 12-15-2017 at 08:54 AM.
12-15-2017, 09:48 AM
#133
Drifting
Overall they wound up with a lower overall ratio including the rear axle, but there are always tradeoffs.
I think the main point of all this technical discussion is to show where current transmission architectures can be improved. There is room for improvement in every single transmission architecture out there. Hopefully the C8 DCT (or whatever it may be) will be state of the art and offer improved feel over the A8, without too many other tradeoffs. I'd love to have the feel of a PDK in my C7 on top of what it already can do.
Last edited by RedLS6; 12-16-2017 at 01:14 PM.
12-15-2017, 04:46 PM
#134
That was my point, the AMG DCT quoted above has the worst ratio spread off all the ones we've talked about (5.39), was only strong enough to utilize a 3.40 first gear, and they made the rest up with a slightly less efficient rear end.
Overall they wound up with a lower overall ratio including the rear axle, but there are always tradeoffs. A non-planetary DCT with a 650 ft-lb torque rating and a 7:1 overall trans ratio with a 4.5 first gear doesn't yet exist.
I think the main point of all this technical discussion is to show where current transmission architectures can be improved. There is room for improvement in every single transmission architecture out there. Hopefully the C8 DCT (or whatever it may be) will be state of the art and offer improved feel over the A8, without too many other tradeoffs. I'd love to have the feel of a PDK in my C7 on top of what it already can do.
Overall they wound up with a lower overall ratio including the rear axle, but there are always tradeoffs. A non-planetary DCT with a 650 ft-lb torque rating and a 7:1 overall trans ratio with a 4.5 first gear doesn't yet exist.
I think the main point of all this technical discussion is to show where current transmission architectures can be improved. There is room for improvement in every single transmission architecture out there. Hopefully the C8 DCT (or whatever it may be) will be state of the art and offer improved feel over the A8, without too many other tradeoffs. I'd love to have the feel of a PDK in my C7 on top of what it already can do.
You guys need to stop making this unnecessarily overcomplicated.
All GM has to do is let the suppliers know the specs of whatever DCT they want, and the suppliers will make it happen.
Don't believe the BS that the Corvette team has spread in the past.
The C7 could have had a DCT.
GM simply refused to pay for it.
And, by doing so, bet on the loyalty and low standards of the "Corvette faithful" to accept and buy an inferior product. ( C7 )
By refusing to fully invest in the C7, GM lost my sale, and many others, to superior product offered by the competition
I believe that GM will not make that mistake again, and that the C8 redesign will be fully funded, unlike the disappointing C7.
Corvette will finally return to being a world class sports car by offering the best transmission available,
like the competition has been doing since 2009.
Last edited by SSsedanM6; 12-15-2017 at 04:49 PM.
12-15-2017, 04:51 PM
#135
You ran up against the same stubbornness about DCT's that I ran up against a few years ago right here on CF. Folks who make completely false statements and spreading innuendo about DCT's vs TC transmissions.
It's one of the reasons I don't spend nearly as much time here on CF as I used to.
Thanks for your posts.
It's one of the reasons I don't spend nearly as much time here on CF as I used to.
Thanks for your posts.
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ByByBMW (12-15-2017)
12-15-2017, 05:55 PM
#136
Team Owner
12-15-2017, 06:21 PM
#137
So, when GM announces their new DCT in the C8, I hope all these people are held accountable for their posts and behavior on here.
Last edited by SSsedanM6; 12-15-2017 at 06:24 PM.
12-16-2017, 01:20 PM
#138
Drifting
The Porsche 8-speed Panamera DCT is one of the best DCTs out there, if not the best. It's a step above the Tremec unit. There are varying grades of DCTs available, and if GM does go this route they should try to compete with these newer boxes, IMO. They're doing it in a transaxle with limited space, and they also need to fit the diff in as well, so it'll be a challenge.
Looking at the leaked pics in the other thread, the transaxle in the powertrain pic could be a DCT based box, just based on the way the back of the transaxle looks.
The transmission controls and shift delays are as big a part of the equation as the transmission itself, and I hope GM offers improved shifting feel here, over the controls in the A8, without giving up ratios or durability inside the box.
lol. Unfortunately, it's not that easy.
Looking at the leaked pics in the other thread, the transaxle in the powertrain pic could be a DCT based box, just based on the way the back of the transaxle looks.
The transmission controls and shift delays are as big a part of the equation as the transmission itself, and I hope GM offers improved shifting feel here, over the controls in the A8, without giving up ratios or durability inside the box.
Originally Posted by SSsedanM6
All GM has to do is let the suppliers know the specs of whatever DCT they want, and the suppliers will make it happen.
Last edited by RedLS6; 12-16-2017 at 02:24 PM.
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thebishman (12-16-2017)
12-17-2017, 12:13 PM
#140
This is the absolute truth. The 488 is even better dialed in than the 458 in my opinion.