[JayTee2019]

Yeah, maybe for others sake, here is the GMC media site:
2019 Acadia: Mid-Size SUV - GMC; 2019 Acadia Denali: Mid-Size Luxury SUV - GMC

The is an error in that 2019 GM chart. I've viewed that previously before and after buying our Acadia and the Final Drive ratio listed for the 2.5L and 3.6L transmissions are reversed. The 2.5L I4 should be 3.87 while the 3.6L should be 3.16. Otherwise. .. . it seems correct.
The build sheet on two different 2019 V6 Acadias I have does show the correct axle ratio.

 

[JayTee2019]

I'll leave that to others. At least, the Limited owners manual is available.

Here is an earlier link to that info - -

GM 6-Speed 6T75 M7X Hydra-Matic Automatic Transmission

The Hydra-Matic 6T75 (production code M7X) is a six-speed automatic transmission produced by General Motors for use in front-wheel-drive-based all-wheel-drive vehicles with a transverse powertrain orientation. Developed in-house by General[...]

gmauthority.com

6T75 M7X tranny used in 2017 Acadia : GM 6-Speed 6T75 M7X Hydra-Matic Automatic Transmission

Gear Ratios
First:	4.484
Second	2.872
Third:	1.842
Fourth:	1.414
Fifth:	1.000
Sixth:	0.742
Reverse:	2.882
Final Drive Ratio:	3.160

 

[Grantv]

So 6T70 or 75? Am I the only one? I am just getting over a cold, maybe my head is thick...

 

[JayTee2019]

So 6T70 or 75? Am I the only one? I am just getting over a cold, maybe my head is thick...

The second gen (not 2017 Limited) Acadia uses the 6T70 in 2017 to 2019 with 6 cylinder as it was in Chevy Equinox and GMC Terrain 3.6L V6 from about 2013(or earlier?) till 2017 as well as a few other GM vehicles.
The 6T70 and 6T75 appear and are essentially the same except the 75 has beefed up internals.
The 6T75 was used in the heavier Buick Enclave, Chevy Traverse, and original GMC Acadia and Saturn Outlook AFAIK.
There have been some running changes in the 6T70/75 along the way since it was introduced.

 

[Guitarjrw]

Another data point for everyone. I have a 2017 FWD Denali model with about 35k miles, we bought it used and has been doing the 2 to 3 flare the whole time, interestingly not enough to where we noticed it on a long test drive before buying. Ours is much more frequent on left turns, I tried changing fluid a few times, running the fluid level slightly low and slightly high, it did seem to occur less frequently with the lower fluid level for some odd reason. I even tried switching from GM Dexron to Valvoline fluid but that made no difference either. Finally had enough and took it to the dealer, they acknowledged the flare but said it’s completely normal for these, they said they haven’t seen any real failure issues on these transmissions since about 2012. While the flare on this Acadia is definitely worse than my other vehicles I will say modern 6-9 speed transmissions all have quirks that drive me crazy. They are tuned from the factory for maximum fuel mileage at the expense of drivability. My f150 drove me insane until I finally got it fixed by using a tuner and a custom tune, obviously the f150 is a much bigger market for tuners than the Acadia so probably not so lucky to get this fixed with a tune.

 

[Grantv]

There was a poster here who did tunes, said he was about ready to get it done for the Acadia 2-3 flare. Poof, unsure where he went.
Mine does the same, and I do think it's programming. I wonder if the tranny is trying to skip 3rd and go 2-4 shift. Makes me somewhat wish my Acadia had the gear dash display.
Yes, modern tranny's are definitely finnicky beasts.
What did the F150 do that was bothersome?

 

[Guitarjrw]

The f150 definitely didn’t have the flare, it was mostly related to shifting to higher gear as quickly as possible for fuel economy. The thing was it took several thousand miles to show up, as it learns overtime I guess. But it got to the point where it felt like a manual transmission in the wrong gear, climbing a hill it wouldn’t downshift until way too late, which caused it to pulsate going up hills. The tune fixed all that but it does get 1-2MPG less. I would guess this is definitely in the program and highly dependent on driving style and conditions, for example I seem to notice it more when my wife has been driving the car for a few days and then we switch, but regardless it does have the flare with either of us driving. I have contemplated trading it in for a Pilot or Highlander but I go in their forums and find similar quirky issues with the transmissions so who knows if anything is better than what we got here.

 

[Jeff O]

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.

Do you guys sell this tune?

 

[Grantv]

Do you guys sell this tune?

They posted 3 times total, last was 9 months ago. Hopefully they reply, but you might have to find them. Post what you find...

 

[atfalf65]

So I finally had another similar year GM vehicle come into our shop(goodyear tire & service shop) that had the same M7U RPO trans that the 2017-2019 Denali AWD has, it was a 2016 Equinox LTZ AWD with the previous generation 3.6L but our trans. I drove it to see what it shifted like - it shifted like should. no hang ups, hunting for gears, and NO 2-3 shift flare! The Equinox trans acted like it should. I decided to use my HPTuners interface to "read" & save the data from the TCM - I also did the same thing from my 2017 Acadia Denali AWD - On HPtuners you can compare two like or same module's data. I have only started to begin to weed thru the shift speed/timing/pressure tables as well as the TCC lockup tables. Lets just say there are way more differences in calibration data than I would have figured there would be, considering the trans is mated to very similar engines/hp/etc. line pressures for upshifts are less on the acadia, they are allowing for torque converter lock up in gears 2/3/4 on the acadia and other differences that isn't programmed into the equinox trans. Im going to analyze it some more, and possibly copy & adjust some of the acadia data using the equinox data and then upload and drive it. FIRST im going to wait until the certified pre owned warranty runs out since I dont want a non GM logged time stamp of a calibration update stored in the module incase I do have take it back in for powertrain warranty issues. My thoughts of the trans issues being related to a calibration problem & not hard parts is further being supported....

 

[JayTee2019]

So I finally had another similar year GM vehicle come into our shop(goodyear tire & service shop) that had the same M7U RPO trans that the 2017-2019 Denali AWD has, it was a 2016 Equinox LTZ AWD with the previous generation 3.6L but our trans. I drove it to see what it shifted like - it shifted like should. no hang ups, hunting for gears, and NO 2-3 shift flare! The Equinox trans acted like it should. I decided to use my HPTuners interface to "read" & save the data from the TCM - I also did the same thing from my 2017 Acadia Denali AWD - On HPtuners you can compare two like or same module's data. I have only started to begin to weed thru the shift speed/timing/pressure tables as well as the TCC lockup tables. Lets just say there are way more differences in calibration data than I would have figured there would be, considering the trans is mated to very similar engines/hp/etc. line pressures for upshifts are less on the acadia, they are allowing for torque converter lock up in gears 2/3/4 on the acadia and other differences that isn't programmed into the equinox trans. Im going to analyze it some more, and possibly copy & adjust some of the acadia data using the equinox data and then upload and drive it. FIRST im going to wait until the certified pre owned warranty runs out since I dont want a non GM logged time stamp of a calibration update stored in the module incase I do have take it back in for powertrain warranty issues. My thoughts of the trans issues being related to a calibration problem & not hard parts is further being supported....

Thanks for this info.

We owned a 2015 Equinox LTZ for 4.5 years which I ordered out new with the 3.6L LFX V6 engine and also wondered what the heck they did in the Acadia to make it shift so rough and unevenly.
The Equinox shifted in what I would call a good, smooth sequential manner. No lurches, flares, unexpected weirdness, etc.
So when we got our new, off the dealer lot Acadia last year I thought it shifted less than ideal.

I agree with all you said and suspected the same. . . . so is good to hear at least some initial info. It makes sense now if they are indeed kicking in the lock up as low as 2,3,4.
I'm wondering with worry also, it they also program some TC slip to try and smooth things out. I know this. . the Acadia transmission temps run higher in any weather than the Equinox seemed to.
Heck, the 8L45 in my 2017 Colorado runs way cooler. In Summer drives we regularly take upstate, I rarely see trans temperatures higher than 130F to 140F in 7 hour drives and even up and down some steep grades for 10 miles or more. In cool temps like now 51F today and lower the last few days. . the 8L45 doesn't even get up to 90F !
When checking the Acadia trans temps around town and the semi rural roads we use, I see 150F to 180F most times.
In Summer if we take a drive to a nearby town about 75 miles away, the Acadia will top 190F to 210 on a hot day.

 

[Grantv]

Also pretty much always suspected programming. People here have had valve bodies or even full trannys replaced with no change. Really only leads to programming.
Even just in my own driving experience though, the flare is only happening in a small RPM shift range, only under certain conditions.
Programming...
Whenever my warranty expires I'll very likely have someone mod the program.
In the meantime, it's really my only complaint about this vehicle!

 

[atfalf65]

I've had upper/lower valve bodies/TEHCM/filter and anything else replaceable aside from the internal case hard parts, and none of it changed a thing. I had a GM TAC case opened, lots of driving logged, data submitted to the engineers, and they were the ones who recommended replacing all of those components. After replacement, was still doing the same thing, they logged more & submitted the data, and then the engineers said" its functioning how it should" and that they were closing the case. The dealer said that its great that I have the extended CPO powertrain warranty so that if anything comes up with the tranny, it will still be coverd.... I also spoke with my uncle, who works in the smaller crossover development team at GM(equinox/terrain/captiva/trax/etc) and he said the engineer who did the programming for this transmission, in our specific platform actually retired shortly after the new body style came out. So technically, GM doesn't have the guy who developed the initial calibration even around anymore to go back and tweak/improve the programming. My uncle also mentioned that the entire team was running behind on getting the 2017 models read to go so there was not near as much testing/refining the powertrain & related systems that they usually have before they release a new body style for full on production. He drove a 2018 denali for a month when it was brand new and admitted that it was one of the worst driving crossovers that he had driven over the last 10 years.

I may dive into tweaking the calibration sooner than I planned. I have a Tech2 and GDS2 GM software at my disposal(Same that the dealers use) so as long as I can always flash the most current stock calibration onto my 2017 before I take it to the dealer for any power train warranty issues, I may dig into making some adjustments & seeing if it changes some of these issues we all are having.

 

[Grantv]

I may be wrong, but if you mod anything, even if you return it to factory settings... they'll be able to tell. Tread carefully.

 

[atfalf65]

I've asked some.of my gmc dealer tech friends and they said everytime a vehicle is programmed at a dealer or by dealer type software which is ACdelco TIS2Web, it creates a time stamp in GM's database as to VIN and when module is programmed. So if this is true, then if I flash it at my shop with GM software, it should make that the most current Cal and stamp in their database since it is an entire web based system. We will see

 

[divotdug]

I may be wrong, but if you mod anything, even if you return it to factory settings... they'll be able to tell. Tread carefully.

Nope, you are not wrong. My son is a service advisor. Pretty much every vehicle these days has at least one black box with all manner of data being recorded. They may not be able to tell exactly was changed but can tell it was changed.

An old wives tale that all you need do is restore the original files and no one will know the difference.

 

[atfalf65]

There is a difference between flashing the stock file with an aftermarket tuner and actually using a GM interface, software and proprietary programing system.

 

[Johnnyg]

I just picked up a used 2017 SLT Acadia with 35k miles and found the 2-3 flare. Never noticed it in the test drive. Oddly enough in my commute there are two left turns on level ground where the flare is very evident and feels to be around 1/2s or so, enough to feel the vehicle to slow. I'd be interested if flashing solves or minimizes the issue.

 

[atfalf65]

I never got around to actually modifying the stock transmission calibration on my 2017 Denali. The wife and I had that vehicle for about 11 months and had the upwards of nine visits to the dealer for various problems which included everything from the transmission issues all the way to a rear evaporator AC core leaking all the way to the shift to park message problem as well as the drive mode selection switch acting up and a month before the certified pre-owned warranty was up we decided to trade it off because we knew that this was going to continue to have problems it would be out of our pockets.

So in January we traded it all for a good deal on a 20 Denali ultimate addition which of course had all the upgrades and improvements to the first 3 years of the new body style. The nine speed transmission is a dream and makes it an entirely different vehicle to drive. They refined the active suspension and it rides even better than our '17 did. Every issue or annoyance that our 2017 had was fixed with the revisions and updates that they applied to the '20 and newer models.

I was losing my faith in general motors because of that 2017 but seeing how they fixed the issues for the 2020 model year it has restored some of my confidence in them. I do feel bad for all of you who still own a 2017 through 2019 knowing that a lot of you will have some of those similar annoyances that gmTAC is going to ignore since those vehicles are already a few years old.

Do I think the transmissions programming and functionality issues are going to be detrimental to the longevity, no. If you're a picky driver and are very in tune with your vehicles and yes it is going to annoy you long term. I do know by comparing those two calibration files that I had read from my 2017 Denali and from the 2016 equinox that they were many differences shift portion and the apply and release pressure sections of the tunes and I am completely confused as to why there was such a large difference from one year to another when it was basically the same powertrain unit.

My uncle who does work for GM's crossover engineering segment did mention that the technician who was working on the transmission calibrations for the 2017 to 2019 models probably did not have enough time invested and fine-tuning and unfortunately that manifested into all of these production vehicles. If you've got the money and can stand some depreciation I would recommend getting into a 2020 or newer because it will change the way you see the Acadia.

 

[Markni12304]

I am on my 3rd transmission on a 2019. Still has the same 2-3 flare issue. I have resolved to just live with it.