My 2015 Z51 A8 has not been shifting properly under hard acceleration. Seems to be hanging up somewhere between gears 5-8, around 60mph 4500 rpms. Anybody had this issue? Dropped it off at the dealers this AM.

 

Are you driving in the "Sport Mode?" I had this issue (only in the sport mode) and everyone here told me it is normal. I took it to the dealer and they said they could not duplicate the problem. I still am not clear as to why this happens, but everyone here says it is normal. Below is the statement from the owners manual that (sort of) explains it. If this happens in other than Sport or Track mode, I would think it is abnormal. The car actually went into the Manual mode automatically, even though the shifter on the console showed Drive, I could see "M" on the instrument panel.


"Sport – Performance Algorithm
Liftfoot (PAL) recognizes
aggressive throttle maneuvers
and holds lower gears for
greater engine braking and
enhanced vehicle control when
not using paddles. (Available in
Sport or Track mode.)"

 

Yes, always drive in sport mode but never noticed it before until yesterday. Has happened twice now. Glad to hear that though. thanks for the reply.

 

You are welcome. I hope they are all correct and nothing is wrong. Let me know what the dealer says about it. Personally, I quit driving in the Sport mode unless I intend on manually shifting.

 

I'll definitely post the dealers response. I'll take your advice and quit using sport mode as well.

 

I'd take it to the dealer, you have nothing to lose but a little bit of your time. It's probably just the performance shifting being activated but you never know.

If the dealer can't duplicate the problem but you can consistently duplicate it offer to drive the car with the tech in the passenger seat. That way if it's something normal when it happens you can say "right there, that's what I'm experiencing" and the tech can say "Oh yeah that's normal, it's the performance shifting holding the gear since it thinks you're driving in a performance manner". or maybe he'll agree it's abnormal and now has seen the issue and has more information on how he can duplicate it themselves.

 

Good advice, thanks.

 

No problem, I'm only a back yard mechanic but I'm a professional programmer and I can say when it comes to duplicating a bug that the user has found it can be nearly impossible from only their description of the issue without watching how they use my system. We watch them use it once and see they did something weird the normal user doesn't do and we go "OOOHHHH!!!" and when we start doing that too we can duplicate, diagnose and fix the bug in no time.

I imagine in the current age of these high tech cars the same thing will be more and more common as more and more of the car is digital and adaptive to the users preferences.

 

Makes good sense. Had the feeling the service writer had no clue how to communicate effectively what I was telling him to the techs.

 

No problem, best of luck to you!

One more thing I'd recommend if you still think there is an issue and they say they can't find anything is to document EVERYTHING you do from the time you start the car until the time the event occurred. Sometimes it's something mundane that you wouldn't think is related in any way that is causing a bug.

I'm completely making this up for the sake of an example of the kind of weird bugs I see sometimes in my applications, but maybe there is an issue where if the A/C is on above setting 4, and the windows are rolled down, AND the car is going over 50 MPH then the car pulls power from the transmission to give to the engine to compensate for the additional drag you're putting on the car and that loss of power causes the transmission to shift slower than normal. It seems like having your windows down, ac on, and going over a certain speed is unrelated to the shifting of the transmission but in this fantasy chain of events you find that it's actually the root cause of slow shifts.

 

Just my .02 but I'm pretty sure from your description that in "Sport Mode and Track Mode" (as you said you were in Sport Mode) what you are thinking is a hanging shift is a computer function called "Performance Shift Active" (as shown on Page 5-44 of your Owners Manual.
When in Sport or Track Mode if you accelerate "hard" as you said you did, you will get a message on the DIC pop-up that says "Performance Shift Active". From my understanding this is a function that allows your automatic in D (drive) to auto select the upper or lower gear for maximum performance in the corners and on the track.
Try this and see if this is what your thinking is a hanging shift:
From a 50/60 roll in Sport or Track mode press the accelerator about 3/4 throttle sharply and hold it there through the initial downshift. In a second or so you should see a message in the center display (DIC) that pops-up and says "Performance Shift Active". Let out of the throttle back to your normal speed. You will notice the transmission will stay in the downshifted gear for 5 or 6 seconds until the computer senses your not going to proceed with performance driving; it will then shift to the appropriate gear for your speed and shift normally again;
Now switch to "Touring Mode", and repeat the same test as above: The trans will downshift and accelerate, but as soon as you let off the throttle the transmission will recover quickly to the appropriate gear for your speed. Also, the "Performance Shift Active" message will not appear at any time.
Hope this helps as I will be willing to bet Lunch (a metaphor) that that is what you're feeling in the transmission, and secondly, unless it a big corvette dealer with experienced techs, they won't have a clue as to what your talking about.
I suppose this was a long way of saying "Normal Operation" and actually a really neat feature on the twisty or the track.

 

I'm sure now you are exactly right. During hard acceleration I'd never notice anything the DIC said so again that sounds exactly like what is happening. thanks for the input.

 

No problem I hope it helps out. I see TN on your avatar. You guys are lucky down there, a much longer driving season than MI and lots of nice twisty mountain roads not far away. Enjoy your car, they are awesome!!!

 

I have to chime and say that I love "performance shift" mode and wish I could make the car stay in it all the time. I suspect the gas mileage sucks but it feels like a different car when it is active.

 

You can cut thru a lot of communication problems at the dealer with a smartphone video, if you can dupe problem. Obviously some problems cant be video'd, but if so, they will consider it valid.

I had the display flicker last year, dealer said "bring it in, so we can see it. Then will order the part". I took an iPhone video ,sent him an email with the video ,and that was good enough for them, they ordered the part and I only had to go in once to get it replaced.

 

batesman

This explanation of your concern is perfect. Don't expect your dealer tech to have any idea of what you're trying to have fixed. There are so many nuances in the C7 operation that are dependent on which mode it's in and how it's being operated that most dealer techs understandably will not be able to determine whether what you are seeing is normal operation or not.

The clue to your problem being normal is the 'Performance Shift Active' message in the DIC. Both the A6 and A8 transmissions do this when in Sport mode and in D. Upon acceleration that is aggressive enough to cause a downshift, when foot is lifted, the trans stays in the gear it's in and the rpms stay raised accordingly for about 10 seconds before automatically dropping back to D. Tapping the upshift paddle will make it return to D sooner.

As a side note, the paddles can be used when the trans is in D to either upshift or downshift without being in M. Play with it. It's quite helpful to use it for passing a car on a 2 lane road by dropping into a lower gear sooner than by just pushing the accelerator.

 

Sounds like exactly what's happening, but completely normal. It's one of the awesome features of the A8, and the primary reason it is so well received at the track.

 

Chevrolet really needs to include a little explanatory pamphlet with the C7 that covers these common customer concerns/questions. This would provide better customer relations and avoid some of the dealer interactions which don't always turn out well since a lot of the dealership personnel aren't that familiar with all of these operating characteristics.

When I bought my first GMC pickup with the Duramax diesel/Allison automatic it included a small three or four page glossy pamphlet with a title something like "living with your Duramax and Allison". This covered things like the Allison's different shift behavior based upon operating temperature and the louder than normal hydraulic fluid noise from its greater fluid circulation. Even if the information can be found in the owner's manual most owners are not going to carefully read and comprehend everything in the manual, particularly since much of it only applies to vehicles optioned in a specific way.

 

I doubt Chevy would do this because there are legal issues in everything they print and it has to pass the corporate lawyers before released to the public. I think we're stuck with the owner's manual for now.

There should be a mandatory reading thread for all of these issues for new owners that post on here thinking their car is screwed up. These posters could automatically be sent this thread so they could have a reference of things that are normal. The thread that is in the stickies above is so cluttered with useless discussion that it takes forever to get to the useful info contained within it.

 

I agree that this should be a "stickie thread." This is at very least a very confusing feature and the manual says a lot of mumbo-jumbo, but does not accurately describe this feature. I have read it several times. I think there are a lot of people (like me) that this would scare the heck out of the first time it happens. I was convinced the transmission was going out.