Is this a future A8 problem
Thread Starter
Instructor
Joined: Apr 2013
Posts: 108
Likes: 28
From: fresno ca
Is this a future A8 problem
own a 15 Z51 with A8 for just over a year getting close to 10x miles. on two occasions when rolling through stop sign at a crawl the A8 slams into 1st gear with enough force to cause my head to hit the headrest. I try to recreate the shift but can't but I have noticed that a more suttle delay shifting into first at rolling stop signs seems to be occuring more often. Is this a sign of problem coming?
Safety Car
Joined: May 2016
Posts: 4,488
Likes: 1,028
From: MN
Greetings from MN! My guess is it's just confusion on the automatic's part. Your car might be trying to decide if you are REALLY going to stop or not. Mine will smoothly go 3 to 1 (skipping 2) if I come to a complete stop. If I am rolling a stop, on occasion, I typically stay in 3. You might be rolling JUST slow enough to shift to 1.
Le Mans Master
Joined: May 1999
Posts: 6,515
Likes: 1,302
From: Windermere FL
My '15 did this from mile 1 and it was quite violent. Quite a few forum members had this from the get-go. GM came out with new tranny software about a month after I got mine and it seemed to get rid of this problem. I am not sure if your car was built after the new software was installed on the line.
Either way a trip to the dealer is in order. But it is unusual that this just started. There were other service bulletins including one with learning procedures that was supposed to fix it, but flashing the new software was easier in my case and worked.
Either way a trip to the dealer is in order. But it is unusual that this just started. There were other service bulletins including one with learning procedures that was supposed to fix it, but flashing the new software was easier in my case and worked.
Melting Slicks
Joined: Jan 2017
Posts: 2,982
Likes: 1,039
From: Georgetown CA
2018 Corvette of Year Finalist
2017 C7 of Year Finalist
The automatic will sense driving conditions (its adaptive) and occasionally jump into a performance shift mode. You can force it to do that by giving a quick blip on the throttle, it should show in the DIC that performance shift mode has been activated and the shifts would be a lot harder and quicker. Maybe that is what happened?
Racer
Joined: Nov 2016
Posts: 497
Likes: 242
My '15 did this from mile 1 and it was quite violent. Quite a few forum members had this from the get-go. GM came out with new tranny software about a month after I got mine and it seemed to get rid of this problem. I am not sure if your car was built after the new software was installed on the line.
Either way a trip to the dealer is in order. But it is unusual that this just started. There were other service bulletins including one with learning procedures that was supposed to fix it, but flashing the new software was easier in my case and worked.
Either way a trip to the dealer is in order. But it is unusual that this just started. There were other service bulletins including one with learning procedures that was supposed to fix it, but flashing the new software was easier in my case and worked.
Melting Slicks
Joined: Mar 2013
Posts: 3,104
Likes: 626
From: Baton Rouge LA
My 2015 did that twice in the first month of ownership, but not violently enough to be a safety issue, just startling. No recurrence in the ensuing 23 months I owned it, and I attributed it to adaptive learning.
Melting Slicks
Joined: Jan 2017
Posts: 2,982
Likes: 1,039
From: Georgetown CA
2018 Corvette of Year Finalist
2017 C7 of Year Finalist
Again, it is an adaptive transmission and depending on how you're driving it could jump into a more aggressive shift mode. Good to try it out on your own by blipping the throttle and confirming that it jumps into the mode. Do it in a safe area, blip the throttle and watch the DIC to confirm it goes into that mode then hit the gas again and let it shift, you'll feel the difference.
Drifting
Joined: Jan 2006
Posts: 1,554
Likes: 158
My 2015 Z51 A8 did the same thing about 90 days after I bought it. Happened a couple of times. I also had the shift bump from 1st to second upon start up a few times after the car sat all night. I ask the Chevy service tech about both items while car was in for oil change.. He said to give it some time as the trans was adjusting to my driving style. I did not fully buy it but did not want to push for trans work on a new car unless necessary. After 6 months those issues went away and have not returned. The trans now shifts great at high or low RPM's. Car could not run any better but it is a mid year built 2015 and I worry that the other A8 issues will show up any time. Probably about the time the car goes out of warranty.
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Thread Starter
Instructor
Joined: Apr 2013
Posts: 108
Likes: 28
From: fresno ca
thanks gentlemen for your observations, I have enjoyed the car for over a year now and these minor shifting delays have becme more obvious to me. You cant help but be concerned with every little glitch when you read all the negative A8 posts almost daily, and to top it off my wifes car is getting a new tranny as we speak and it also had a delay shifting in first gear. At least with a 15 I have 100,000 warranty. Thanks again for your posts, going to keep an eye on it.
Pro
Joined: Sep 2014
Posts: 701
Likes: 179
From: Muskoka ontario
OP, my 2015 started doing a very hard downshift , 3 to 1, during a rolling stop as you described. It started at the 1500 mile mark. As I got more miles on the car it happened more frequently as well as other drive line issues starting to show up. The first time I took it in for service the TCM software was updated and the first TC change out was done. After that the hard 3 -1 was fixed. I don't know if it was the software upload or replacement TC that fixed the problem.
My suggestion would be;
1) ONLY take it to a dealer who services lots of Vettes,
2) If the service writer wants to jump at the TC right away ask/suggest if you can have the TCM software looked at/updated and try that first. That should be no skin off their nose as in addition to other things the TC bulletins call for software verification as a first step anyhow as part of the TC replacement.
3) most important of all , do step 1.
Hope this helps, good luck, keep us posted.
My suggestion would be;
1) ONLY take it to a dealer who services lots of Vettes,
2) If the service writer wants to jump at the TC right away ask/suggest if you can have the TCM software looked at/updated and try that first. That should be no skin off their nose as in addition to other things the TC bulletins call for software verification as a first step anyhow as part of the TC replacement.
3) most important of all , do step 1.
Hope this helps, good luck, keep us posted.
Le Mans Master
Joined: Feb 2014
Posts: 9,426
Likes: 2,634
From: Gilbert Arizona
Similar but opposite...
I have a similar. but opposite problem with my A8 GS.
Since I don't like starting in 1st gear from a light or full stop, I paddle into 2nd gear when I come to red lights and stop signs. However, if I don't come to a 100% complete stop, and I paddle into 2nd, it shifts like a Mack truck and it feels like it shifts via sledgehammer. I'm very careful now to make sure I am at a complete stop before I upshift into 2nd.
I have not experienced the reverse, where it shifts violently while downshifting.
Since I don't like starting in 1st gear from a light or full stop, I paddle into 2nd gear when I come to red lights and stop signs. However, if I don't come to a 100% complete stop, and I paddle into 2nd, it shifts like a Mack truck and it feels like it shifts via sledgehammer. I'm very careful now to make sure I am at a complete stop before I upshift into 2nd.
I have not experienced the reverse, where it shifts violently while downshifting.