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DCT Reliability & Cost Concerns...Anyone else?

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  • DCT Reliability & Cost Concerns...Anyone else?

    I am still a little dead inside because a manual won’t be offered. Not just because of the driver engagement lost, but also because the long term reliability and maintenance of a DTC could get ugly outside of warranty. It won’t stop me from owning the car (because it’s so perfect otherwise) but it makes me think, especially the long term reliability and costs outside of warranty as I tend to keep my cars a long time rather than trading them in before warranty expiration (I am not a baller like that 😀)

    Here’s my concern: Corvettes have traditionally been high torque cars...I am curious how the ZO6 gearbox will handle the punishment. Other DCT cars in the market have significantly less torque than what we are used to seeing in the Z variant of Corvettes.

    Some examples:

    Audi R8 - 413 lb-ft
    GT3 - 339 lb-ft
    GT2 - 516 lb-ft
    Ferrari 488 - 561 lb-ft
    McLaren 600LT - 457 lb-ft
    McLaren 720S - 568 lb-ft

    I think this this is another reason why Chevy is moving to turbocharging the next ZO6 (rumors anyway). I think it’s going to be very different. If the next Z approaches torque numbers of its predecessor C7Z and ZR1, I would be very interested to know how the DCT was designed to shoulder that load...and if it will be able to shoulder it long term so I don’t have to spend $20k for a transmission out of warranty down the road.

    This is is the main reason I am highly considering the base car or grand sport version (if they make one) rather than a Z variant....a first for me.

  • #2
    I think it all depends on the design of the DCT. The one I had in a Volkswagen was bulletproof. On the other hand, Ford has used a DCT in one of its smaller cars and it has been troublesome. I would have preferred that GM source its DCT from ZF.

    This is all part of the reason I wait until the second year of read the feedback from the early converters.


    • #3
      The fact that Tremec is making it puts my concerns to rest. They are the only company that makes big horsepower/torque handling transmissions for the big 3 muscle cars. The TR6060 is bulletproof. They also already make a DCT so it isn't new to them. My wife just had a Jeep Cherokee with a ZF 9 speed (not DCT) that self destructed at 62k miles. It was under warranty, but new transmission, lines, cooler, and anything that touched was replaced. Getrag makes the junk Chinese transmission in Mustang and have seen failures in under 5k miles. So for me, if I were bet money on anybody to make a solid box, it would be on Tremec. They get it when it comes to big power requirements.


      • #4
        My experience is with a Golf R DCT and as a member on a very active Golf R forum, many of whose members appear to be thrashing their cars. The DCT trans has come across as extremely reliable with zero complaints, even in highly modified cars. The MT version of the car comes in for a lot of complaints in comparison.

        Think of the DCT as being like a manual trans that has perfectly executed, shock-free (or at least gentle) shifts every time. So if there are problems I don't believe they are going to be gear related. Maybe actuators or electronics, but not basic mechanical bits.

        In this I'm agreeing with Phil above with respect to Tremec.
        2020 C8 Corvette.D.O.B 2/03/2020
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        • #5
          Most wet clutch DCTs are highly reliable. It's the cheaper dry clutch design used by Ford that's trashed the reputation of DCTs. Ford programmed in extra clutch slip to mimic the behavior of TC automatics, which resulted in excessive heat when in stop and go traffic. The excess heat glazed the clutches and damaged the TCM module which was conveniently mounted on the DCT housing so it could overheat with the rest of the transmission.

          Ford's senior development engineer on the DCT project warned them it wasn't ready for production but the bean counters declared it a success and cashed in on some of Ford's reputation. Once in the field, those bean counters calculated it would be cheaper to replace clutch packs and TCMs than to actually fix the problem.

          Two more observations:
          1. Aftermarket tuners claim to be able to fix Ford's DCT by programming in quicker, more positive shifts, thereby minimizing clutch slip.
          2. The same getrag tranny is used in some French cars reliably. Europeans are more acclimated to manuals than Americans, so those French engineers haven't programmed in excessive clutch slip like Ford's have.

          Regarding the Tremec DCT transaxle in the C8, I'm not very worried since Tremec are a supplier of transmissions for heavy duty trucks and even military hardware. Their engineers understand what is required to handle high torque. And the DCT controller will probably be amazing because Tremec bought the Belgian firm Hoerbiger Drivetrain Mechatronics for their DCT control IP, the very controllers used in Ferarries, McClarens, and AMGs. We have a marriage of the best of both worlds in the C8's transaxle and as Tadge said, they spent as long developing the DCT as they did the rest of the C8. As illustrated by Ford's DCT debacle, the programming can make or break a DCT, so it's reassuring to know they spent so much time on it.


          • #6
            In the C-8, we are getting the DCT practically for free. If it was a Porsche you would pay
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            • #7
              Tadge did say in one Video Interview that there was as much time spent on this DCT as the whole other car combined. This tells me that this transmission , that was specifically built for the C8 may be bullet proof. The 7 speed Tremec DCT for the GT500 , has a more limited production number than the C8 , TREMEC , has to get this right with the transmissions they are selling to GM and will be selling in this model and future models . And as noted , this is not this is not the first rodeo for tremec. For those of us that would have rather seen a ZF transmission I am sure with the volume that GM is going to purchase they certainly has their choice between ZF and Tremec. Remember Porsches volumes are much lower. .


              • #8
                GT-R has a wet clutch DCT also. People routinely run Full Bolt On (FBO), Intake, Downpipe, exhaust, injectors, fuel pump, tune, E85, on the stock transmission. They are putting down ~600 awtq, meaning actually torque to the ground. I would not be concerned with the DCT with a stock LT2, or even mildly modded for that manner.

                Built DCTs in the GT-Rs are running 1k - 3k awhp, with 1k+ torque to match.

                While I know DCTs are new to most, and people have unfortunately heard the well published failures, these have been on bargain bin DCTs. I have faith that GM did it correctly the first time with their bespoke Tremec unit.


                • #9
                  Im not worried in the slightest...this is a supplier based product to gm specs and todays computer controls interacting between engine and transmission gives me no worries towards the c8 s dct.


                  • #10
                    I would like to shed some light from a former insider. When I was selling new Corvettes I received a Corvette specialist book every year from Chevy. They gave the dealer personnel some info they didn't tell the public. Now I don't know what the drivetrain accept criteria is today, but when I was selling, to be an accepted vendor of a transmission (manual) for Corvette your transmission had to do 100 drag strip passes in a row wide open throttle and no lift speed shifts on every one with no failure. That's insane, trust me Chevy will not tolerate frail or weak parts on this car. I remember holding a pinion gear in my hand out of a C5, it looked like it came out of a tandem dump truck rear end it was so big. Tadge touched on it when he said bespoke to meet the Corvette duty cycle, he just didn't get into what the goes into an acceptable duty cycle.

                    One of the lines that Chevy knew about was Corvette buyers said going to a Chevy dealer to buy a Corvette was like going to K-Mart to buy a diamond. They know what they've got.
                    Last edited by Phil1098; 07-27-2019, 02:59 PM.


                    • #11
                      I too, feel they most probably have worked any major issues out. They just have too much to loose if this new tranny wasn't dependable. A mistake like that for this new C8 could be catastrophic for the Corvette brand!

                      That being said, if I were one of those on the fence about the future higher horsepower C8's versus the base engine, and no intention of tracking the car, I would certainly stay with the base engine...for many reasons. Just my opinion.
                      Last edited by George; 07-27-2019, 04:27 PM.
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                      • #12
                        I think the biggest issue they are going to have with the DCT isn’t reliability but changing what the average Corvette buyer expects. One thing it will not do is mimic the slush box which could throw a lot of people off. Under some throttle conditions the shifts can be abrupt compared to a TC automatic. Most of the time the shifts will only be noticeable by the change in Engine tone so the abrupt changes will have some thinking their car isn’t working correctly. I suspect GM will have special training for the Corvette specialists to pre-condition the buyers in what to expect, what’s normal and what isn’t.

                        Remember, the majority (well over 70%) of Corvettes built in the last 20 years have been TC automatics. A large portion of the current Corvette owners haven’t driven a manual for decades, if ever, they really won’t know what to expect. Once they feel the virtually no loss of forward momentum under acceleration and perfectly rev matched down shifts they should be willing to overlook the peculiarities.

                        Manual drivers will need to learn new techniques too. Downshifts are what’s the most different but the perfect rev matching going up or down means the car may not react to the shift the same way it does when you control the clutch engagement. However, it’s quite entertaining once it becomes 2nd nature. If they get it right you may find your fastest lap time in D, that’s something some may not be able to come to grips with initially


                        • #13
                          Mark, even though I come from 53 vehicles with a manual trans in a row (now have four of them), I am looking forward to learning how to drive a DCT properly. Thank you.
                          GBA Black; HTO Twilight/Tension interior; Z51 & Mag Ride; E60 lift; 5VM visible carbon fiber package; 5ZZ high wing; FA5 interior vis CF; ZZ3 engine appearance; 3LT; Q8T Spectra Gray Tridents; J6N Edge Red Calipers; SNG Edge Red Hashmarks; VQK Splash Guards; RCC Edge Red engine cover; VJR illuminated sill plates. Lifetime, annual contributors, and 23 year members of National Corvette Museum. Home is the beautiful Pacific Northwest.


                          • #14
                            I have never had a car with DCT mostly been standards. But I assume with Tremec behind this and GM's first mid-engine a lot of thought has gone into this. I will miss the connectivity that a standard gives but it would be hard to beat the fast shifting of the DCT. Looking forward to the experience.


                            • #15
                              That’s my attitude too, e.g., embracing the future (after 53 manual trannys in a row).

                              GBA Black; HTO Twilight/Tension interior; Z51 & Mag Ride; E60 lift; 5VM visible carbon fiber package; 5ZZ high wing; FA5 interior vis CF; ZZ3 engine appearance; 3LT; Q8T Spectra Gray Tridents; J6N Edge Red Calipers; SNG Edge Red Hashmarks; VQK Splash Guards; RCC Edge Red engine cover; VJR illuminated sill plates. Lifetime, annual contributors, and 23 year members of National Corvette Museum. Home is the beautiful Pacific Northwest.