Transmission hopes for the ME

[Plasboy]

Im seeing that most think or hoping that the ME will have a DCT. I too hope one is available but would like to see an automatic too. From what I’ve read DCT’s can be a little jerky around town and would rather have an auto for the way we use our cars.
Could they use the ten speed automatic and who would make the DCT. Tremec and ZF both make a DCT that is robust enough for most applications or will they build their own.
What are your opinions?

[John]

Good questions and input. I can only answer a small part of them. You are correct that the first generation of the DCT’s were often clumsy and jerky, especially at lower speeds and low RPM. In fact, I remember Tadge saying those exact words at the 2013 BASH when he was defending the C7’s not offereing a DCT.

However, so many improvements have happened to DCT’s in the last few years, and the best ones out there now do not have either jerkiness nor clumsiness. The most consistent answer as to what we can expect from the DCT as to its manufacturer is that it will be a ZF, 7 speed, DCT. We have several members who have driven this ZF trans in their ME’s and said that it is very smooth — love it a lot. There are a minority who disagree, and have said they are sure it is a Tremec, 7 speed, DCT.

One thing for sure, is that GM will not both offer a traditional automatic, such as Corvettes have had for many generations, and also offer a DCT. Why not both?

The complexities, and therefore costs, of matching a motor’s performance characteristics with the transmission, ECM, traction control and all other safety systems, are immense. So therefore are consequent testing and development costs, for in the U.S. every single trans and vehicle combination must separately tested and certified in many areas, including emissions requirements.

Hence, since every birdie that has whispered to me, has said that DCT’s are what we will be getting in our ME’s — as have the vast majority of forum posts (FWIW) and the auto media.

Conseqeuntly, a DCT is the best trans info that we can now conclude.

I have not answered the question about the other elephant in the room, how come with 22% of C7 buyers choosing to buy a manual transmission, we are not getting an additional manual transmission option. Very strong opinions on this issue, with many saying, “just you wait, for we will be getting a 7M option for our ME’s.”

[Plasboy]

Yes I can see where the added cost would be a reason not to offer an automatic. Good luck to those who still want a manual.

[OnPoint]

GM holds a patent for a DCT trans that utilizes a torque converter. The TC is only unlocked at low speeds - the purpose of which would be to "smooth out" the operation at low speeds. It then locks up as speeds increase over that of a few mph, and the trans then operates like a tradition DCT.

I don't have information whether or not the ME will utilize this. I just find it interesting that GM patented that tech, and when I recalled that, I wondered if they'd use that tech to smooth transitions into and out of cylinder deactivation on the engine as well. Unlock the TC to go from V8 to V4 or vice versa, and then lock it once the transition is made.

Don't know if they'll do that or not. A contra argument to that is the fact Lambo now has cylinder deactivation on its engines, and they utilize a straight DCT.

[John]

That is very informative and valuable information OnPoint! Thank you very much!

I doubt I am alone in wanting something which works extremely well, is extremely smooth in all its transitions. Beyond that, and this could well be my ignorance, I do not have a preference for whether it is a pure DCT,or a DCT that also utilizes a torque converter.

[OnPoint]

Yeah, with advancements in software and computing power of the controllers, they may not need. It's interesting tech, though.

The Corvette faithful who have enjoyed their autos, haven't had to deal with any low speed jerkiness in those transmissions. My bet is they'd have a pretty dim view of a DCT that did that. GM no doubt knows this and will work to avoid it. It can obviously be done without a TC as Ferrari with their latest, and Porsche with their latest transmissions have demonstrated. Might be yet another item that could argue in favor of ZF as the manufacturer, as they and Porsche together have been down this road.

[John]

I am biased in favor of having a ZF DCT because ZF not only has that DCT, but also has a special product for motor mount vibration dampening, another one for rear wheel steering, and another active kinetic control (AKC) suspension system, so if there some combinations of these products on progressively more powerful versions of the ME over successive years, having them all come from one manufacturers gives the greatest opportunity for seemelss integration of all these products. Further, as we know, almost everything is computer controlled to some degree, and having different components potentially work on the same company’s based sensors, transmitters, relays, and computer software helps the integration of such complex products/systems.

[OnPoint]

John, that makes a lot of sense. For all your stated reasons (and the fact IMO ZF builds great stuff), I hope they go that route.

[Plasboy]

How often do the DCT transmissions require a clutch change?

[John]

I have read conflicting info on this and would love to know others’ thoughts. However after reading and seeing the attached video (should one wish), I think just like a clutched-pedal manual, it depends a lot of the driver. I am sure there are some DCT’s needing clutch replacement horror stories, but we have known about drivers who have had to replace their clutch on a clutched-pedal-manual way prematurely too.

*Don’t put the transmission in neutral when you come to a stop. There’s no need to do this. You may think the clutch will be partially engaged and wearing out, but the system will be sure to disengage the clutch (while keeping first gear pre-selected).

*Don’t take your foot off the brake when you’re on an incline. The clutch may attempt to hold the vehicle. Unlike in an automatic transmission where you have this slip absorbed by the torque converter, this will directly cause wear on the clutch. Depending on the design, the effects can be even greater with a dry clutch, which has no oil around it. Wet clutches tend to be able to take more heat, however dry clutches are more efficient, robs less power (used on sports bikes), it weighs less, and often requires less maintenance (there’s no clutch fluid, it’s all electronically actuated on Hyundais). For Hyundai, owners are asked to inspect the fluid levels every 37,500 miles on the DCT, but there is no set time to replace fluid.

*Try not to spend much time inching forward (especially while towing or on steep inclines). Stuck in traffic on a hot day, crawling up an incline at low speeds, or towing. In these scenarios, it’s best to allow yourself enough gap to get up to speed, so the clutch pack can fully engage. At low speeds while partially engaged, the clutch will heat up and can wear faster. It’s never ideal to slip a clutch, but they are designed to take wear and tear. This advice is to simply have the clutch last as long as possible.

*Upshifting while braking, downshifting while accelerating. Need to understand the logic behind the system to understand why shift delays might occur. For example, driving on the highway, 4th gear, hit the brakes because someone cuts you off. Upshift and it takes longer than usual. Well because you were on the brakes the transmission might have assumed you were going to downshift next. Coming to a light, if it’s red but turns green, the system may have been attempting to disengage the clutch knowing that you were coming to a stop, so there may be a slight delay in getting power.

*Don’t hold the brake and throttle long if launching the car (launching your car in general is a bad idea for longevity, but if you were to do it, know what’s happening internally). This will cause the clutch to wear, all of the heat from the engine is going into the clutch (if it’s engaged, depending on the car). From Hyundai - “The engine speed should rise and the clutch should go to a stand by position. The clutch may try to engage and if it identifies no vehicle movement it should reduce the engine speed and hold that speed until the accelerator pedal is released.”

What have others heard about DCT’s needing their clutches replaced?

[NewYuriCity]

I remember seeing the patent for that torque converter DCT, very clever design. I wouldn't be surprised if that was used on the base/introductory model, but I kind of hope they'd drop the torque converter on HiPo models to save weight.

[John]

Just skipped over to the major BMW forum, and many are saying, DCT’s last the life of the car — and we all know that when there is an issue, disproportionally, everyone with an issue who has ever been on a forum, will hop on and post their problem, yet few routinely post the positive..

Went to the Porsche forum re the DCT life, and not seeing problems noted there either, though I did see the statement that Porsche has tested its DCT launch control and pronounced it good for 1,000+ launches.

[Plasboy]

Don’t know what they consider the life of the car to be but that’s pretty impressive if it will do 100,000 to 150,000 miles without replacing. Haven’t had a manual transmission in a long time so I don’t know how that compares to current manuals.

[JB]

Dry dual clutches are garbage... fords almost lost all focus sales because their dry dual clutch was horrible.

saving money on a dry clutch design is money not well saved..

porsche utilizes wet clutch and their drivability is top notch.

[John]

Thanks. I did not know that Porsche DCT’s, considered the best in the world, use wet clutches. I just quickly checked, and at least some (maybe all) Ferrari DCT’s use wet clutches — as do the BMW’s DCT.