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Our personal 2016 developed a nasty 2-3 upshift flare around 50k so we took it into the dealer this will be 1 of 3 trips.
1) The dealer pulled the transmission opened it up found wore clutches so they replaced anything that seemed damaged, this trip took around 2 months before we got the vehicle back. After a week of driving the upshift 2-3 flare was back full force back to the dealer for round 2.
2) This trip in they pulled transmission just as trip one and found the same exact issues so long story short another month and half passes by before we get the vehicle back. Guess what, right around a week of having it back the upshift 2-3 flare was back once again off to the dealer but a different one this go round.
3) This dealer keeps the vehicle a few days and calls reporting that all their test show that the transmission is doing just what GM had built it to do so we pick it up. This is when I decide to start looking at adjusting the 2-3 upshift calibration. Let me say this up front we own a small tuning shop and our background is in GMs so we know a thing or two about tuning GM transmissions and this isn't a sales pitch just what we were able to do to stop the 2-3 upshift flare. After several rounds of adjusting oncoming and off going pressures, shift speed, rpm/mph and some torque management we were able to stop the flare.
While GM will not fix the issue we have access to a very well mapped TCM thanks to HPT and with some knowledge it can be fixed.
 

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I believe what you're saying, I think tuning can fix this. But are you able to fix cars a distance away?
 
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Our personal 2016 developed a nasty 2-3 upshift flare around 50k so we took it into the dealer this will be 1 of 3 trips.
1) The dealer pulled the transmission opened it up found wore clutches so they replaced anything that seemed damaged, this trip took around 2 months before we got the vehicle back. After a week of driving the upshift 2-3 flare was back full force back to the dealer for round 2.
2) This trip in they pulled transmission just as trip one and found the same exact issues so long story short another month and half passes by before we get the vehicle back. Guess what, right around a week of having it back the upshift 2-3 flare was back once again off to the dealer but a different one this go round.
3) This dealer keeps the vehicle a few days and calls reporting that all their test show that the transmission is doing just what GM had built it to do so we pick it up. This is when I decide to start looking at adjusting the 2-3 upshift calibration. Let me say this up front we own a small tuning shop and our background is in GMs so we know a thing or two about tuning GM transmissions and this isn't a sales pitch just what we were able to do to stop the 2-3 upshift flare. After several rounds of adjusting oncoming and off going pressures, shift speed, rpm/mph and some torque management we were able to stop the flare.
While GM will not fix the issue we have access to a very well mapped TCM thanks to HPT and with some knowledge it can be fixed.
Crazy that GM won’t fix this and offer to reflash affected cars.

They replaced my entire transmission and it’s much better now but I can see it just getting worse over time as it’s already developing a small blip on the 2-3 shift.

Still has a tremor at idle that drives me bonkers too and was hoping it was transmission related. But alas it is not and maybe fuel related?? Anyone else’s Acadia (2017 and newer) shake at idle/park/neutral? Feels like mini earthquakes as long as it’s sitting and then while driving is 100% fine.
 

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Mine is so quiet and smooth I have to look at the tack to make sure it's still running - seriously.
Yeah I assume that’s how it should be.. wondering if a fuel filter or something random is off. Maybe that’s what causing my 2-3 shift flair too as the brand spanking new trans is doing the EXACT same thing as before.

Either way car is a 2017, 35k miles and should not be having these issues.
 

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Yeah I assume that’s how it should be.. wondering if a fuel filter or something random is off. Maybe that’s what causing my 2-3 shift flair too as the brand spanking new trans is doing the EXACT same thing as before.

Either way car is a 2017, 35k miles and should not be having these issues.
Assuming it's a 6?
 

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I just had our Acadia out for a 35 mile run on semi rural highway with stop signs here and there. So there were many up shifts. I took note each time of all shifting from normal take off to a couple "spirited" take offs.
All shifts were smooth and if I wasn't looking at the tach I could not really tell when gears were changed.
This was on a cold start of 27F and 2,925 miles on the odometer.
Also, had to drive at 30 to 40 MPH around town for about 5 miles at the end of the run with a few traffic light stops.
All was well. Hope it stays that way.
 

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Mine only occurs with light-medium throttle, and between 2500-3000RPM or so. Biggest problem with that, is that's the sweet spot for daily commute driving. So I hit the flare at least once a day.
Spirited driving provides spirited shifts. Lower RPM shifts are uneventful.
 

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Our personal 2016 developed a nasty 2-3 upshift flare around 50k so we took it into the dealer this will be 1 of 3 trips.
1) The dealer pulled the transmission opened it up found wore clutches so they replaced anything that seemed damaged, this trip took around 2 months before we got the vehicle back. After a week of driving the upshift 2-3 flare was back full force back to the dealer for round 2.
2) This trip in they pulled transmission just as trip one and found the same exact issues so long story short another month and half passes by before we get the vehicle back. Guess what, right around a week of having it back the upshift 2-3 flare was back once again off to the dealer but a different one this go round.
3) This dealer keeps the vehicle a few days and calls reporting that all their test show that the transmission is doing just what GM had built it to do so we pick it up. This is when I decide to start looking at adjusting the 2-3 upshift calibration. Let me say this up front we own a small tuning shop and our background is in GMs so we know a thing or two about tuning GM transmissions and this isn't a sales pitch just what we were able to do to stop the 2-3 upshift flare. After several rounds of adjusting oncoming and off going pressures, shift speed, rpm/mph and some torque management we were able to stop the flare.
While GM will not fix the issue we have access to a very well mapped TCM thanks to HPT and with some knowledge it can be fixed.
It's all wonderful that you can tweak the software. I'm not so sure the hardware is up to the task.
 

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Mine only occurs with light-medium throttle, and between 2500-3000RPM or so. Biggest problem with that, is that's the sweet spot for daily commute driving. So I hit the flare at least once a day.
Spirited driving provides spirited shifts. Lower RPM shifts are uneventful.
.
I normally apply enough gas under my usual driving style in the 2,300 to 2,500 RPM range. I mentioned spirited driving only as another way to see if it did or did not occur then. And 2,500 to 3,000 RPM is pretty spirited take off in our Acadia.
For the drive I took today... I applied more than usual pedal and it shifted at 3,000 to 3,500 RPM.
Is there a lag or loss of speed when you get the flare you mention? If there is any in our Acadia it is so slight I do not notice anything in lag of shifting or momentary loss of speed.
 

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I'll watch my shift RPM points tomorrow... 1-2 is usually lower I think, 2-3 around 2500, but often closer to 3000
Highway onramp higher.
 
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P.S. no lag or loss of speed I think. If anything it feels like a surge. But that might be imaginary from the motor speed increase...
 

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P.S. no lag or loss of speed I think. If anything it feels like a surge. But that might be imaginary from the motor speed increase...
I think you already said how many km on your Acadia . . . couldn't readily find it. .
It's odd some seem to get or notice flare early on and others not into many more miles.
I have read on other GM vehicle forums that changing the trans fluid early and as often as every 30K to 40K miles rather than wait for the recommended mileage points.
That seems to be prudent. Wife has a little 2017 Chevrolet Sonic LT (10K miles) and daughter has a 2014 Sonic and we changed daughters trans fluid at 78K miles and it was totally black. We did 2 drain and fills of 5.4 quarts based on what came out and then refilled the same amount. Later checked the level after reaching proper operating temp.
Member @rbarrios here has a Traverse and 2 other GM vehicles and changes his fluids regularly. Seems to work well for him.
So . . . with the new Torque Converter Clutches that these new 6 speeds have in them it also seems prudent to do early changes what with the allowed slip under certain conditions programmed into them.
 

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My 19 just turned 6000KM, so less than 4000 miles.
I think you already said how many km on your Acadia . . . couldn't readily find it. .
It's odd some seem to get or notice flare early on and others not into many more miles.
I have read on other GM vehicle forums that changing the trans fluid early and as often as every 30K to 40K miles rather than wait for the recommended mileage points.
That seems to be prudent. Wife has a little 2017 Chevrolet Sonic LT (10K miles) and daughter has a 2014 Sonic and we changed daughters trans fluid at 78K miles and it was totally black. We did 2 drain and fills of 5.4 quarts based on what came out and then refilled the same amount. Later checked the level after reaching proper operating temp.
Member @rbarrios here has a Traverse and 2 other GM vehicles and changes his fluids regularly. Seems to work well for him.
So . . . with the new Torque Converter Clutches that these new 6 speeds have in them it also seems prudent to do early changes what with the allowed slip under certain conditions programmed into them.
Just turned 6000KM, so a bit under 4000 miles. Might be a tad early to need a fluid change... :(
 

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My 19 just turned 6000KM, so less than 4000 miles.

Just turned 6000KM, so a bit under 4000 miles. Might be a tad early to need a fluid change... :(
Wow. . . . only about 1,000 miles more than ours. Ours is just FWD and wonder of there is some difference between that and AWD transmission/engine programming? Just a thought, besides the obvious hardware differences.
Is difficult to keep track and note what drive folks have that are having this issue.
 

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Wow. . . . only about 1,000 miles more than ours. Ours is just FWD and wonder of there is some difference between that and AWD transmission/engine programming? Just a thought, besides the obvious hardware differences.
Is difficult to keep track and note what drive folks have that are having this issue.
Between this thread and another I’m fairly confident it’s narrowed down to the 2017-2018 FWD Denali Acadia software that has issues. Lucky me.
 

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Between this thread and another I’m fairly confident it’s narrowed down to the 2017-2018 FWD Denali Acadia software that has issues. Lucky me.
Add me. . . lucky here also with our 2017. However, we just have an Acadia SLT-1. Not sure why that would make a difference.
The idle on out Acadia has always been smooth and notice not roughness to it. The engine does make the usual fuel injector ticking, but idles smoothly so far.
 

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Between this thread and another I’m fairly confident it’s narrowed down to the 2017-2018 FWD Denali Acadia software that has issues. Lucky me.
2019 AWD... started around 2500 miles or so.
 
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