I don't understand the issues with the transmissions. If the problems are existential, it seems every DCT should fail. 100% of them. If it is a systemic design problem, 3 years later why has it not be re-engineered? BG has installed 100,000 DCTs and an disheartening number have had problems. But many not most. Truth, I'm not much of a mechanical wizard, but I just don't get the logic here? Knock on wood three times, our 2022 built 10-2021 is one of the 'most'. To date at least.

 

The problem is a lot call them a transmission failure when in reality it's a transmission issue. So it quits working, OK, that's not good, but did it fail? If it goes in and gets a flush and works again then it hasn't failed. It has a weeping leak, has it failed? No, it has a weeping leak. An axle seal got nicked, did the DCT fail? No they replaced the axle seal and didn't damage it this time. They had a supplier that left some grit in a component that was supposed to be cleaned out first, those usually require a valve body and or a flush, but the DCT didn't fail. They did make a design change half way through 2021 and changed the case design and fluid pan. So they have addressed issues as they have come along.

 

One of the threads somebody posted their Facebook exchange with a Tremec employee. Sounded like they were getting parts from a sub-supplier that had excess debris from manufacturing that wasn’t cleaned. That would make sense given some of the symptoms people have posted and GM’s fix is to start with a flush.

Workmanship and quality issues generally just affect a small subset of parts which is probably why it’s not 100% guaranteed to fail, but persist among enough transmissions you hear about them on forums.

Some transmissions were replaced due to leaking castings, but that’s a different issue being counted as a DCT problem.

 

because they are mechanical devices. They all fail.

 

What makes me smile is knowing mechanical failures occur on a bath tub shaped curve. A bunch when they are new, flat across a normal life, and then a bunch at the end because they are worn out. Based on this proven understanding of mechanical failures, why is it such a mystery to people that EVERY manufacturer includes a warranty for at least a few years when new. Why is that? Because they KNOW new or not, man made assembled stuff gets screwed up. It covers the first part of the bath tub curve. We all want and expect new things to be perfect, but the people that make them don't, otherwise they would never offer any warranty because there would be no need for it.

 

I've owned a dozen cars and probably have driven a combined million miles. Never had any transmissions fail. Failing transmissions is definitely not the norm.

 

^^^This^^^
In 2013 Dodge changed engine block casting suppliers for the V10, and within miles (literally, some failed as people drove off the lot with the Dodge Viper) people were reporting spun bearings (some, not all). In essence same story, factory was getting blocks from a sub-supplier that had excess debris (oil galleys) from manufacturing that wasn’t cleaned. If you were on the forums at the time, the sky was falling even though it was a very small percentage....fwiw

 

And I had a 2014 Jeep Cherokee with a ZF 9 speed that never rolled another foot under its own power at 62,000 miles. Had to have a new transmission. It happens.

 

Tremec started assembly of the DCT from Mexico where my two Tremec C7 manual transmissions were made to a new $50-million, 125,000 ft2 Wixom, Michigan, facility. The first C8 was delivered in February 2020, 1 month after the start of the Pandemic. Hmm, expect new employees, who had to be trained to make this complex transmission may have been a factor in some of the clogging issues due to debris.

For those interested in "how complex," I condensed only key points from a 3 page article by Don Sherman in SAE International magazine below:

Inside Tremec’s Corvette dual-clutch transmission by: DON SHERMAN 2020-01-23

Corvette’s TR 9080 reveals the densest package of shafts, gears, actuators and electro-hydraulic servos to be found in any modern automobile. 5 aluminum castings support the 2 clutches, 6 shafts, 5 synchronizers, 24 gears, 5 shift rods and multitude of bearings.

Add 3 electrohydraulic control bodies, an assortment of speed and position sensors, and a master electronic controller managing every DCT aspect. A mechanical multi-plate limited-slip differential is in the base Corvette and complex electronic controlled eLSD in the Z51 performance package.

The 2 normally open wet clutches are positioned concentrically. Hydraulic pistons rotating with the clutches force them into engagement when commanded.

As in manual transmissions, all main shaft gears are permanently meshed with mating gears spinning on the counter shaft. No torque is delivered until 2 of the 5 triple-cone synchronizers are moved by a computer-controlled actuator.

PS: My DCT has been working flawlessly for 17 months (knock on wood!) Probably not made on a Monday morning or late Friday!

 

The simple answer is that every transmission in every brand of car/truck will have some issues in some vehicles.

The DCT tranny in the C8 is spectacular. Like every other mechanical part, there will be issues that occur.

But....every time a problem crops up in the C8, it gets blown up way out of proportion on this forum. We hear too much from the complainers.

 

With every part a certain ratio of "fails" is deemed acceptable (meaning cost efficient) by management. (trust me, I've an ugly anecdote overheard between two Ford attorneys in an airport lounge verifying this)

My issue with the transmission is why GM chose to source it with Tremec when many others had considerable experience with exactly the type transmission desired, and the chosen firm had to start from scratch (my understanding).

 

Simple...Low Bid...

 

Turns out, you didn't understand. Tremec is in bed with one of the best mechatronics companies and has been for almost a decade and they already made some of the best manual transmissions out there. The acquisition allowed the marriage of the transmissions they know to the mechatronics Hoerbiger knows and then ten years to sort it out. It's WHY the TR9080 is so good in performance right out of the box.

 

Tremec bought the company that makes DCTs for Ferrari. That means they bought that company's expertise. Hardly starting from scratch.

And of course a certain percentage of failure is deemed acceptable. And not just in the auto industry. The cost of zero defects in complex devices is typically far higher than the cost of doing warranty repairs or replacements. What makes more sense: Budgeting 'x dollars' for repair and replacement, or budgeting 'x times 3 dollars' and doubling production time to avoid warranty replacements. Remember, you, the buyer, ultimately pay that cost either way.

 

Agreed 100%. Some failure is expected with pretty much any engineering.

I think the thing with the DCTs that makes it so alarming is that if it fails you could be stranded. Also doesn't help that our current situation means parts/replacement isn't readily available. And the current situation also means getting a loaner is a crapshoot.

Nothing worse than spending $80k on a car, that's in the shop for 2 months, and you're paying for a rental out of your own pocket.

 

But it will given enough time and mileage.

 

All the manufacturers who have developed dual-clutch transmissions have lots of early teething problems. They are a bit of a time-bomb.
The problems are either design issues, or manufacturing/quality-control issues. There is a mix of both in the DCT graveyard.

But I agree, why didn't GM go with the 3 or 4 companies who have been doing DCTs already for 5 to 15 years....

 

^^^
Quoting from the Don Sherman article referenced in my previous post:
Tadge Juechter notes, “Our customers began requesting a dual-clutch automatic transmission [DCT] several years ago. ” Searching the globe – read Europe – for a suitable DCT, Juechter’s team found none with sufficient torque capacity to survive behind the lively LT2 6.2-L V8 planned for the all-new 2020 mid-engine edition of GM’s reimagined sports car."

Yep the LT2 pushrod small block may lack the high tech design of high twisting engines but it has lots of Torque. It's torque that defines the trans capability not it's high rpm hp! Yep it has the same peak torque as the C8 Z06 LT6 670 hp DOHC engine! It also has to meet the life expectancy of a typical street engine not just the short term demands of a mostly Track car! Suspect cost was also a factor.

 

If you read posts #13 and #14, they did. All this armchair quarterback second guessing is so easy to do when there is absolutely zero inside knowledge of what happened and why.

 

^^^
Yep agree! Per my post #18, Don Sherman is one of the best automotive writers, has an MS in Mechanical Engineering as well as a race car driver. He understands what Tadge is saying in an interview and can ask tough questions. . Tadge also knows what his engineers are telling him and can also ask tough questions (he has degrees in aerospace and mechanical engineering.)

So agree, all those "who think they know better" than GM talented folks should consider their own sports car design skills and accomplishments!