You're assuming someone will buy an A8 in the ZR1 I see..... 
I know I know.... they say the automatics are faster.... Hmmmmm.....
I know I know.... they say the automatics are faster.... Hmmmmm.....torque converter
- Thread starter xviper
- Start date
So my 17 Z06 has the 3 spd "bump". I am told that it is torque control lockup (TCC) we are feeling.
Thats nice to hear BUT not every A8 Corvette experiences this sensation. I went back to Spring Mountain and had the lead instructor go out on the track and we played for probably 1/2 hour with no bump. He also said he has never heard or experienced this phenomenon.
I will push a dealer to shove a new transmission ECU into my car because this is a software problem.
I have talked to a tuner back east and he says he can tune the TCC out until 4 gear I wont feel the bump-no kidding. Would be interested in this if GM backs the warranty-yeah right.
Thats nice to hear BUT not every A8 Corvette experiences this sensation. I went back to Spring Mountain and had the lead instructor go out on the track and we played for probably 1/2 hour with no bump. He also said he has never heard or experienced this phenomenon.
I will push a dealer to shove a new transmission ECU into my car because this is a software problem.
I have talked to a tuner back east and he says he can tune the TCC out until 4 gear I wont feel the bump-no kidding. Would be interested in this if GM backs the warranty-yeah right.
Good on ya Gordy. Please keep us in the loop as although I am M7, there are a lot of members who are A8 and will be really interested in your ideas and how you make out.
Hey guys, sorry I haven't posted anything in reference to the weird shift lately. Have had it to a US dealer for the MRC upgrade and showed him the 2-3 shift situation and he thought it was irregular but not a big issue. I haven't finished complaining but I need a dealer to hook up a tool and go for a drive so he can manually apply TCC (or watch when TCC applies) to make sure this is what it is. I think I am going to find that this is a software issue and it may be hard to convince someone to change a trans controller to see if that changes the situation. BTW trans has been reflashed twice and it hasn't changed. Next chance to do this is mid July as we are going to Winnipeg with the Meet in the Middle group.
Thanks for the update Gord.
There was a fellow on here who had quite a few things changed by his dealer over this however the issue remained. It’s on one of the threads on this subject. I’ve never heard of anyone getting this full resolved. Seems to be more randomly more prominent in some of the A8s and almost nonexistent in others.
I’ve driven a 17 A8 Stingray and noticed it almost immediately. It was a loaner car so I didn’t pay much attention to it.
Look forward to see you at MITM.
D
There was a fellow on here who had quite a few things changed by his dealer over this however the issue remained. It’s on one of the threads on this subject. I’ve never heard of anyone getting this full resolved. Seems to be more randomly more prominent in some of the A8s and almost nonexistent in others.
I’ve driven a 17 A8 Stingray and noticed it almost immediately. It was a loaner car so I didn’t pay much attention to it.
Look forward to see you at MITM.
D
In Feb 2017 while in Florida I took the car to Stingray Chevrolet in Plant city where it was diagnosed as needing a TC replacement, which was the third TC. I also snagged the "bump" while accelerating in M3. The shop foreman hooked up his computer to the car and we did a test drive.At the point where we felt the M3 bump the computer showed "TCC apply" at that same moment. He consulted with GM TAC and they confirmed the bump was in fact TCC apply and normal.
Fast forward to my 2018 base A8 built late June 2017. One of the first things I did was to test for the bump while accelerating in M3. It was present but not a noticeable as in my 2015.In fact, if you did not know what you were testing for it might actually not be noticed.
Regarding the Feb 2017 TC replacement, the part number of the new TC was the latest iteration and the new tranny fluid that became available late 2016 or early 2017 was used. I only put about 3000 miles on the car before I traded it on the 2018 and for that period of time the transmission performed much better, smoother shifts and no harsh 1-2 shift first drive of the day. There were other issues with the car that prompted the trade but it does look like the latest iteration of the TC combined with the new fluid seems to have made a difference. I suspect that is the reason that on other forum boards I don't recall seeing owners of A8's built post Feb 2017 reporting TC replacements . I have noticed at least a couple of posts wherein the owners reported driveline issues that were diagnosed as "TC failures" and having got their cars back with a replacement TC the original snag was still present. I assume this might be the result of a dealer just not knowing how to properly diagnose a driveline snag and arbitrarily throwing a new TC at the car as this has been a significant C7 A8 issue.
Just wondering, when you were at spring mountain and you were testing for the "bump" accelerating in M3 were you in a base A8 car ( non Z51, non GS, non Z06) ???
The reason I ask is when I was at Stingray Chevrolet in Plant City FL for my third TC replacement I also snagged the M3 bump. The shop foreman who did the test drive with me in my car ( base A8) did feel the bump and his computer showed it occurred at the same moment of TCC apply. We then tested two other cars that were from the used car lot. One was a base A8 and it had the bump. The other car was a Z51 and it did not have the bump which we tested for about six times. The shop foreman followed up with GM TAC and they told him only the base A8 has the M3 bump, which is normal. They told him the Z51, Z06 are different in that they have an elsd and different TCM software.
It would be interesting to see if any forum members with a Z51,GS, or Z06 have the bump or if only A8 base equipped cars are reporting the M3 bump.
Also I did post that he M3 bump in my 2018 base A8 ( built late June 2017) has a very slight M3 bump compared to my 2015. In my 2018 if you did not know what or how to test for that condition you probably would not notice it at all.
Not sure if anyone has ever got a resolution to the issue yet but I have a 2015 Z51 and starting getting the hard jerk when moving from park to drive. I always noticed a bit of a delay since I got the car but never paid too much attention to it but now that it's jerking fairly hard and I started noticing some issues in the first few gears where they just don't seem that smooth in both upshifting and downshifting. However in manual mode it seemed better, anyway I brought it to the dealer due to the recommendation from a performance shop who did some research and noticed that this issue is all over the US forums and there are several technical bulletins related to the A8 transmission which includes a 2016 software update, to replace the stator shaft support and finally replace torque converter. The dealer was actually well informed and noted that they have seen a lot of issues with the A8 transmission in several of the vehicles not just corvettes but at some point in 2016 it looks there were several part number changes such as the torque converter along with the stator shaft support. The dealership mentioned that in their experience so far the least effective resolution was the software update and in basically all cases the issue was mechanical. Thank the corvette gods the dealership is corvette friendly and has now ordered me an entire new transmission with all the updated parts and is just doing a complete replacement under the warranty program. Cost of the A8 8L90 transmission on its own is $4600 so I feel like I dodged a bullet. Should be in late next week and a few days to install so once I get the car back and drive it a bit I'll let everyone know if the issues are resolved with a complete transmission replacement.
Thanks odin. Mine is M7 but through the C7 years there has been several threads and numerous posts regarding A8 problems and to my knowledge, many if not most probably are still looking for answers. Good info.
You should be fine with the new transmission. It will include the latest iteration of the Torque Converter and the new transmission fluid. My 2018 , built late June 2017 incorporates the aforementioned and the drive line is night and day different than what I had in my 2015, August build 2014, which was a nightmare. The 2018 shifts are fantastic and butter smooth.
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