Higgs Boson

Chuck there have been new flashes for the A8. Torque converter clutch stuff mostly. I have not seen any changes to driver demand table or shift points. TCC shudder, drivetrain clunk and improperly torqued shaft bolts (on trucks).

I ended up trading my truck on a 2016 Mustang GT so I am playing with that a lot now. I got tired of dealing with the A8!

red 1

Well the gm engineer didn't show up or return the dealerships call so I called the GM cust service number, after being put on hold by two reps that ended up being hung up on I reached the third rep and started a case number, I found out about all they do is call the dealership and discuss the problem so they haven't been much help yet, they said they would call me back monday. Wish I had never sold my dependable C5 if this one ever gets fixed I may get out of Corvette ownership after years of having one. this C7 has ruined my opinion of GM!

1EasyStep

Start collecting all of your service orders. The dealer told me everything is kept electronically, but that turned out to be a lie the day I asked for all of them. Luckily they were able to send someone to some warehouse to fetch hard copies as the law requires they keep the carbon copy for 3 years. It was a huge hassle and took them a week to produce though. So just make sure you have as much evidence as possible.

If you do decide to file lemon law, the only time you can count without your vehicle is time it was actually being worked on. For instance if you drop it off on a Friday and the service department is closed on the weekends you cant count that, nor holidays etc. Also if the car is driveable but just sitting in the parking lot waiting to be serviced you cant count that either, since technically you chose to leave it and could have driven home. I even went so far as to sneak back to the service area and take pictures of it on the lift without wheels and such as proof that my car was genuinely undriveable.

0Chuck CoW

What model year did you have and what years are you certain about updates?

I regularly check that stuff with new model years and I can't recall any updates..... Fill me in if you remember.

Every time I calibrate something new I always read it out first and then TIS flash it and log the updates.

I like to have the old calibrations so I can compare and then, obviously give the customer the

new latest greatest cals to build my tunes with.

Let me know which ones and I'll check.

Thanks
Chuck CoW

Higgs Boson

I don't have the numbers anymore, it was a 2015 6.2 silverado.

david.a8.z51

I have a 15 z51 with no issues. Most amazing shifts ever in an auto. I believe the horror stories are rare.

BooSSted

Two guys I work with have 15 Silverado's; both are having issues with their transmissions. One actually had his replaced but the issue is still present.

louispe

Unless I get the RPM to 2.5K, I routinely run into shifting problems moving from 1st to 2nd (2016 3LT Z51 M7)

JMBLOWNWS6

Ive had two updates on my 15 GMC Denali truck. I can now say with the second flash it is good to go. I was getting ready to ditch it already. But looks like GM got the **** together. Or I just got lucky.

BooSSted

Is the solution a tune, Chuck CoW? Or is there something mechanical going on? I was pretty set on the A8 but don't want GM to place the blame on power adders rather than their product.

Higgs Boson

It's in the tune

0Chuck CoW

YES, Agreed.

I've heard of the Vettes having issue, but I never really noticed it.

EVERY tune I do, I update to the latest software as there is no reason to tune old stuff....

Most of what I've been seeing is Trucks that have the problem, but no Vettes.


Most updates occurr, especially in new or first model years... That's where most of the updates happen.

One of the reason's why I strongly advise my AutoCal device for MAIL ORDER TUNES is that the device

will always permit me to UPDATE (or we call it FULL FLASH) UP to the newest software or even BACKWARDS to

older software if necessary. I can build the files here and AutoCal will SAFELY change the software in your ECM and TCM

and that's not something that most of the REMOTE tuner tools can do.

Some of them even have problems flashing the same tune safely.

I've seen here on the forum too many times some of these poor handheld tuner customers frying or bricking ECMs

and that's just a big waste of time.

That will never happen with my tool.

Stay TUNED with AutoCal!
Chuck CoW

Watertown Rick

My 2016 Z51 A8 rough shifts 2-3 in manual mode while in track or sport or touring mode. It shifts 2 to 3, then about 1/2 second later it feels like it drops to neutral and then goes back to 3. Is this as similar software programming problem that you folks are experiencing?

yonks8365

Sounds like it could be clutches going. Ive had that problem. Ive had a couple replacement trans. Due to the clutches going out. Do you do a lot of spirited driving?

Watertown Rick

Yikes - Hope not. It did It since driving it off the lot. It now has 1200 easy break in miles on it. But your diagnosis fits. So far the A8 has only seen part throttle mild shifts while breaking the car in . I want to put a scan tool on it and see if the shift solenoid has been commanded to shift 2-3. If the solenoid command is solid, that is it stays commanded while it slips and reengages then I will check the pressure. If it holds as well then it is a clutch as you say. It may also be a weak accumulator or bad check valve some where. I will let you know what we find. It does it in manual mode but not in Auto so I am still hoping it is software and not hardware. It is driveable and we are quite busy in our shop so it will take a while to get to it. Thanks

yonks8365

I had 2 trans go with less then 1600 miles on both of them. Easy driving. Both cases it was the clutches. One trans it would try to shift to neutral in between shifts. The dealership can find out pretty quick by using a scan tool if you don't have hp tuner or efi live.

Watertown Rick

Thanks - Did yours do it in all shifts or just one shift like mine in the 2-3 shift?


Does this point towards one clutch pack for the 2-3 shift? My apologies but I do not have a service manual yet.


Mine does not slip under full throttle shifts, only part throttle in Manual I get this drop in and out in the 2-3 shift. When in drive everything is smooth. So the difference between Auto and manual makes me think software.


Sorry for all the questions. I am starting to think it is time to get off the computer and plug in the scanner and take a look at the shift solenoid commands. Thanks again.

yonks8365

I had one Trans that would do it from the 2-3 and 3-4 shifts. I had another that would do it from the 1-2 only.

Watertown Rick

Thanks again. I am booking an appointment to get it scanned at the dealership. Your info will help focus the tech on what to look for. I will let you know the outcome. It may take a few weeks.

Watertown Rick

I have finally had a chance to go out for a drive using my scan tool and here is what I have found. It is the Torque Convertor Control (TCC) locking up late depending on speed and drive line torque, while in manual mode and shifting 2-3. It seems in 1 and 2 the TCC does not lock up at all. After the 2-3 shift, the TCC commands the torque convertor to stay locked up thru 4-5-6-7-8 . So it is only in the 2-3 shift that you notice the TCC commanding a lock up after the 2-3 clutch has engaged feeling like a slip or intermittent shift. By the way if you are under 25 mph and shift 2-3 under light throttle, the TCC will not lock up. If you full throttle shift 2-3 there is no TCC delay. So it is only under part throttle that the TCC locks up late after the 2-3 clutch, the time varying depending on drive line torque, throttle position, and speed. The dealership advised they have seen 3 other cars the same and involved GM for a solution. GM currently says it is what it is.


So now at least I know it is the TCC locking up late depending on what the software decides to do and not the 2-3 clutch slipping.


We are hoping GM will come up with a better control algorithm on the TCC during the 2-3 shift but for now we know at least the mechanical bits are functioning as intended.


Hope this helps out.