So, I thought I imagined it the other day but I was able to duplicate it a couple times today. When in drive in sport mode going about 15-20 and I pin the throttle, when the car shifts from first to second it smacks the rev limiter before shifting it actually makes me lurch forward in my seat.
Have any of you experienced this?

 

What are you thinking is the rev limiter? When I do street drags sport or track the car shifts at 6500 which is basically redline.

 

Never, you are doing this in drive correct? so it downshifts to 1st when you floor it and when it up shifts to 2nd it hits the rev limiter first? have you been able to eyeball the tach to see if its over 6500 rpm?

 

Correct, I am in drive and yes it downshifts to first then instead of shifting at 6500 to second, to my eyes it appears to go just beyond maybe 6700 then briefly cuts power then shifts. I looked at it twice when it did it and it was definitely a little above 6500.
I’m not in launch mode or anything and traction control is all active, not sure that should matter.

 

Normally these cars shift under WOT conditions in Drive a little early, like 6400 rpm, the fuel shut off is 6600 rpm, so you are definitely hitting the rev limiter. Have you tried a 2-3 WOT in drive shift by itself to see if you whack the rev limiter there also. Maybe a dealer can do a scan or relearn process? Still have the factory rear tires on the car? and have you had the car since it was new?

 

I did and it seems 2nd to 3rd we’re fine. It does have the factory tires with 6,400 miles. I am not the first owner. I have an appointment in a week and a half for carpet and now I am getting a frunk open warning so I guess I will add this to the list.

 

So it only does it on the 1-2 shift at WOT. It probably will do it in all 3 modes, touring , sport, and track. It will probably stump the dealer also, hopefully they have access to a tech expert on the DCT programming and can explain the condition accurately. Make sure your service writer or the service manager knows and understands exactly what your are talking about. Its going to take a good tech that can handle your car to duplicate the WOT 1-2 shift by itself at redline in drive. Good luck. BTW, I was a Chey tech and a Chevy dealer service manager.

 

Thanks for the feedback. I am going to take it out tomorrow and make sure it’s not doing it from 2nd to 3rd. After all this back and forth I am wondering if it was doing it there and not 1st to 2nd. However it shouldn’t do it in any gear shift. I know it’s going to be a pain trying to figure this out. Maybe once it sleeps tonight it won’t do it again lol!

 

Mine does it too... I assumed it was because of the superchsrger or losing traction at shifts and wheels spinning

 

this might be the reason ^^^
my 2023 Stingray w/ headers and cat deletes did this one time on the 2-3 shift.

 

So took it out this morning and it did it and was the 2nd to 3rd shift. Did not do I it again, tires were cold as it was only about 43 degrees. I don’t understand though why, you would figure the slipping of the tires would happen when it upshifts to third so lower in the rpm range, not when the clutch should be letting loose to drop rpm to go into third. Does that make sense or am I *** backward in my thinking?

 

Try and not over think it, just study what is exactly happening. Is the car shifting at WOT at what RPM precisely, it should shift just before 6500 RPM. If the RPM goes higher than 6500 rpm and then hits the rev limiter and then shifts, its not right period. I have 7000 miles on my C8, I have done plenty of WOT in drive and let it shift itself passes going thru gears 1-2, 2-3, 3-4. I have made many 1/4 mile passes down the track also and never does the car shift beyond 6400 rpm and never hits the rev limiter . Even if you spin jumping on the gas while in 1st gear, the trans will still up shift at 6400-6500 RPM . The only way to hit the rev limiter during shifts are if you are in manual mode and are paddle up shifting to late.

 

Not really over thinking it. It’s definitely missing its shift and going above 6400. I’ll let the dealer try to sort it out.

 

If you do not normally drive in this manner, then you would be in an area that the control system has not seen yet. This is something that the trans adaptive learning should eventually eliminate.

 

i can guarantee you it happens. I never drive in manual mode... And I have what he is describing happen to me on occasion. Not every time but absolutely enough to notice it and notice the similarities to his experience.

 

No, adaptive learning shouldn't make the car shift late (past it's programmed shift point). There's something wrong with the car and it sounds like it is easily duplicated. Whether the dealer can diagnose the problem is a different question. Good luck.

 

Where is this adaptive learning feature documented? I know about driver influenced gear selection "Aggressive driving will influence both the upshift and downshift points in all modes......Criteria which have influence are: driving mode, accelerator, brakes, lateral, and longitudinal loading......Changes in gear selection behavior due to aggressive driving can include: ‐ Downshifting early with higher rpm’s during aggressive braking (i.e. entering a corner) ‐ Altering upshifts while experiencing lateral acceleration ‐ Not upshifting when the accelerator is released to avoid unnecessary shifts if the accelerator is re-applied ‐ Recognizing sporty driving and anticipate upcoming corners with the appropriate gear selection entering and exiting." But the vehicle will exit this feature and return to normal operation after a short time when spirited driving is no longer detected.

There is also some re-programming of the transmission control module if the module or transmission or some transmission components are replaced. That procedure calls for "Transmission Control Solenoid Valve Characterization Programming". "The solenoids in this transmission require unique performance characteristic data in order to function at maximum efficiency. This data is programmed and stored in the vehicle transmission control module (TCM). When a transmission assembly, TCM, solenoids or clutch are replaced during service, the performance characteristic data for the solenoids must be retrieved from a web server oecloud repository and reprogrammed into the TCM." The description involves obtaining a specific transmission identification number and retrieving data from the cloud - does not sound like it is "learning" the transmission - but rather looking up previously stored data that is specific to that transmission. The process will also "read the VIN from the engine control module (ECM) using the multiple diagnostic interface (MDI) and then retrieve the applicable genealogy data tree from the cloud. This data tree accesses the original characterization data so that it may be updated with the new component information. The system acquires characterization data for the given TUN/PUN via the cloud and updates the genealogy tree. The TCM is updated with the correct solenoid characterization data, and the cloud is updated with the new genealogy relationship." This sounds like GM maintains an exact record of what your car has, and had.

It would not surprise me if there is some adaptive learning in the transmission (other than the driver influenced gear selection) but I can't find any documentation about that.

 

I assumed the reference to "adaptive learning" was actually referring to those things you described, where the car changes its behavior based on your driving style. As I said, that should not account for "banging" the rev limiter.

 

That's what I thought too - but I'm open to whatever is accurate. I was thinking that there were early 2019-2020 verbal discussions where Tadge or someone said the car will actually detect your driving style and change its behavior. And that maybe got interpreted to mean a long term adaptation. However after seeing the explanation in the Owners Manual about driver influenced gear selection, it was my guess that the verbal discussion was about that feature. I can't find evidence of anything else. Its also discussed in the manual as "performance transmission" and "performance shift" in addition to driver influenced gear selection.

 

Upload the pdr data to your computer or you can even watch it thru the dash display after you sense it happening, then record it with your phone. I've only bounced off the rev limiter when I tried a shorter drag radial, and it's clear as day in the recorder. Take that evidence to the dealer so you don't have some knucklehead out beating on your car to try and replicate it.