PA in CA

Hi gang,

Anyone have fault code 071100 pop up on their GT? My GTC had the code pop up in July, had it checked and cleared and it just popped up again. Car is under extended Fidelity warranty, dealer is saying they want to do a pin test and if that doesn't resolve it, it would need a transmission replacement. Dealer said they have seen it happen once before. Thought I would ask here if anyone has run across this. Glad I bought the warranty!

Case1906

I have not, but this is a tranny problem involving an oil temperature sensor with an electrical fault. I think at least the TCU has to be replace. Good luck with the repair. Let us know the outcome.

PA in CA

Looks like it was a loose pin connection. Easy fix

PA in CA

So the error message came back. Bad sensor in the transmission. The fix: transmission replacement@ 20k

buy the warranty!

PA in CA

Well they installed new transmission on Tuesday. As I was driving home, approx 3 miles from dealer I received the error “ reverse not possible error”, so I turned around and dropped it off. Got the news today that the replacement transmission is bad and it needs a new one.

I have had this car 4 months and most of that time it’s been in the shop.

contacted Mercedes customer care to see what options I have. At this point I am not even sure I want this car.

Acta_Non_Verba

Hi PA,

I am really sorry for you that you're having this experience. Everyone's experience is a personal one and I can't blame you for being disappointed in this car. It would spoil me for sure. Hope you have better luck from here then maybe get out from under it. As painful as it is, I hope you keep us up with the outcome here.

All the Best,

Acta

Acta_Non_Verba

Hi PA,

It's probably not much of a consolation for you. The Tremec DCTs they put in the C8 Corvettes and the MC20 have an abnormal failure rate too. And practically no service just like this DCT. Pull the whole transaxle and replace it. Unfortunately, units always seem to be on back order so owners' cars end up sitting disassembled in dealers' back rooms for weeks on end. I guess be glad it's not a Tremec.

This is the most recent one from a member on one of the Corvette forums just this morning...(Happy Holidays, huh?)

C8 Corvette owner:
Well, today while making an emergency run to the store, my 2021 2LT C8 dropped its 4th TRANSMISSION in 10,781 miles. The first two they pawned off as bad valve bodies caused by clogged solenoids. The third one was a new 2022 unit. It only lasted 3,000 miles. After I raised hell over losing 3 transmissions, they installed a transaxle from the 2023 MY cars and said it had a fix for the earlier issues and I shouldn't have any problems. It went 4,800 miles or so until today. The car made a loud bang and a shudder at about 30mph and the A8 won't shift higher than 3rd gear.

I'm starting to seriously reconsider the 3LT HTC I have on order (due to arrive between April and August '23). Never in my life have I had a car that completely bricks transmissions like this. It's just insane.

FWIW, I have followed the break-in procedures to the letter each time they've replaced them. In fact, the majority of my ownership has been in some form of break-in or another due to the frequency of failures. I don't track the car, it's bone stock. I live in a rural area and the car rarely sees any stop and go traffic... altogether very easy miles. I'm just at a total loss.

Best,

Acta

thebishman

That’s ****ty luck, Acta for sure.

The original Tremec DCTs in the C8 suffered from a ‘porous case’ issue, so there were slow leaks noticeable on the transmission case. That hopefully has been rectified.

Next up was solenoids going bad from debris during the break-in period eventually causing one set of gears on a particular shaft to malfunction due to the solenoid/valve body sticking. (I remember the GR6 in my ‘09 GT-R could have suffered from this; luckily it didn’t happen). GM is now recommending a specific ‘flush’ procedure to clean the debris and changing out the DCT fluid in order to mitigate this solenoid issue. They also are allowing dealerships to actually replace damaged solenoids if the above procedure doesn’t cure the fault instead of replacing the DCT en masse iirc.

I’d be super pissed off having to be on my 4th transmission in a relatively new car that hasn’t been subject to even any ‘hard’ driving. However: the C8 is a massive change from previous Corvettes, using pretty much brand new components so as a previous C7 Z06/7 owner I’m not surprised in the least. (Also, so much about how one’s repair comes out is dependent on the dealership having top-notch Corvette specific techs; one reason why I believe Corvettes should be sold/serviced in their own, stand alone outlets, not mixed in with the rest of the Chevrolets getting serviced).

I sold my GTR two years ago now thinking I’d be buying a new C8 Z06/7 to take to the track. What with Covid; supply/demand issues; the chip shortage and the greatly prolonged introduction of the car on the part of GM, I’m now looking at an extended wait unless I want to drop $50K-$100K over MSRP on one, which is the height of idiocy for a Corvette no matter how fantastic it might be. Best now to wait; let the bugs work themselves out and for the car to hit MSRP.

Acta_Non_Verba

Hi Bish,

Yeah, I'm a little gun shy on the C8. I had one on order in Oct 2020, but cancelled it before the build became active. I don't regret that decision. Yes, the troubles on the Tremec DCT went from porous cases to contamination from the factory to bad solenoids, none of which seem to have ever been solved. Although I don't hear many porous cases anymore so maybe they solved that part. Completely failed DCTs continue for the same reasons 3 years into the model build so doesn't appear to be an issue for GM. Some of those cars will be coming off warranty, then it's on the owner.

From my C6 experiences where a large percentage of LS2/3s had defective harmonic balancers and GM would just keep replacing them never addressing the bad manufacture on the balancer itself. Some owners had as many as 4 replaced on a few years. The only out was to go aftermarket. To my knowledge GM STILL replaces them with the bad balancers, only now everyone is on their own nickels, no more warranties on C6s.

I just returned from the Phoenix Auto show. They had a white Z06 there along with a white 70th anniversary C8. Although I like a flat plane crank motor a lot, too many "new" things on it for me to be interested.

Best,

Acta

PA in CA

So I also learned that the replacement transmission that just failed wasn’t “new” it was reconditioned. I blew my top. Mercedes said that’s what all their warranty replacements are and that reconditioned didn’t mean used but rather a trans that failed on the production line and was pulled, checked, fixed and then used as a replacement. Transmission is “new” as it was never in a car, dynoed for tested and confirmed as 100% working. Well it lasted 3 miles before 1st gear failed. The dealer test drove it after the instal and it passed ,it it failed as soon as I picked it up.

2nd transmission is in route from NJ but that will also be a reconditioned unit.

Still waiting on a call back from MB customer care and one of my asks will be truly new transmission plus…..

stay turned

first world problems but I’m not a happy customer. Will be curious as to what they do, if anything, because I bought car from an independent exotic dealer, not an MB dealer, and car was out of warranty. I’m just glad I bought the platinum Fidelity warranty. My local MB dealer and the warranty co have been great and no issues with them at all. They are doing everything they can and treating me as if I bought the car from MB of Walnut Creek

AMG 17GT

Are the Z06 transmissions any different?

Acta_Non_Verba

The Z06 gets a beefed up (M1M) version of the Tremec TR9080 DCT. More torque for the Z06 FPC motor. I will be interesting to see if the same TR9080 problems follow on to the Z06 platform. Hopefully not. The Z06 is promising, but this would put a stigma on it.

2023 Corvette Z06 Gets Improved Dual-Clutch Transmission (gmauthority.com)

thebishman

Pretty sure it has an extra clutch in it, and obviously the ratios are different. However it’s not like GM needed to beef up the size of the internal components too much I’d guess since the car isn’t a torque monster.

Edit: As always; Acta to the ‘rescue’! lol

Acta_Non_Verba

Hi PA,

Very interesting on the reconned units being used as field replacement units. This is not a high production part and with variations on top of that, so I imagine they are using a pretty strict JIT build schedule. My experience in manufacturing doesn't completely jive with the statement they gave you. In my experience, units that fail in production are cast aside, there isn't a lot of attention given to them (in terms of time, labor hours dedicated to revival) even if there is an attempt to repair what failed to reuse, but just my experience. It might be completely different here. They might have a dedicated repair station so don't take my comment as anything more than just casual.

I am following with interest in how the story ends for you so hope you keep us updated.

Good luck and hope it works out for you,

Acta

thebishman

I would never imagine Mercedes taking the time/effort to ‘repair’ a new transmission on the line during the build; surely they would just return it to Getrag(?) or whomever builds the DCT transmission.

I can however believe that DCT’s that have failed and been replaced at a dealership post build, (obviously) are returned to a central location where the failure is diagnosed and repaired so that the transmission is then in stock and in country ready as a refurbished replacement.