GMC Acadia Forum banner

81 - 100 of 184 Posts

·
Registered
Joined
·
36 Posts
Well **** there goes my idea of trading my FWD in for an AWD in hopes of the flare issues going away.

Maybe I’ll consider a Durango to replace the Acadia.
 

·
Registered
Joined
·
35 Posts
And yours is doing it also I assume? Sorry, 70+ posts...
No worries, it’s a lot to sort through. Yes I’m having the same issue. I started noticing it around 3000 miles (and I’m now at 24k+ miles). I’ve had them look at the transmission a few times - and they can’t seem to “notice it”. I got a video of it the other day where the RPMs jumped as it shifted- just haven’t had time to take it back yet (getting a little jaded with having to take it in for service. Mine was in the shop for 3+ months for an unrelated issue shortly after I got it).
 

·
Registered
Joined
·
909 Posts
3 months!!!! Dang, sorry...
 

·
Registered
Joined
·
2,636 Posts
Well **** there goes my idea of trading my FWD in for an AWD in hopes of the flare issues going away.

Maybe I’ll consider a Durango to replace the Acadia.
I have an AWD '18 with 22k miles and have experienced no flare issues. I don't think it is all that widespread an issue.
 

·
Registered
Joined
·
909 Posts
I have an AWD '18 with 22k miles and have experienced no flare issues. I don't think it is all that widespread an issue.
V6 or 4?
 

·
Registered
Joined
·
3 Posts
No worries, it’s a lot to sort through. Yes I’m having the same issue. I started noticing it around 3000 miles (and I’m now at 24k+ miles). I’ve had them look at the transmission a few times - and they can’t seem to “notice it”. I got a video of it the other day where the RPMs jumped as it shifted- just haven’t had time to take it back yet (getting a little jaded with having to take it in for service. Mine was in the shop for 3+ months for an unrelated issue shortly after I got it).
We'd love to be able to answer more but until we hear back from Admin about vendor we can't get into much.

When yours flares is it close to what I have posted below?

Here are some screenshots from the 2-3 upshift flare we caught while data logging.
Shot 1 is showing the 2-3 upshift starting note that the vertical line is at the point in which the C3 clutch starts to engage, also note throttle position 40% and rpm right around 3K. **This throttle input % and rpm is the only time ours would flare.
9217

Shot 2 shows peak flare up to roughly 3,600 rpm.
9218

Shot 3 shows that the shift is complete.
9219


(mod edit - Pic size reduced for thread. Click on pic for full-screen view.)
 

·
Registered
Joined
·
909 Posts
speleos, please don't remove the posts by Mag's Tuning. At this stage at least I feel he is only helping solve a problem, not advertising.
That said, should we call you Maggie? :cool:
Mine I'm sure is a bit lower in RPM, otherwise very much the same. 40% throttle sounds about right, always the same RPM range (mine I'd say 2500-2600, then flares to close to 3000). Never happens under heavier throttle or lighter.
 

·
Registered
Joined
·
3 Posts
speleos, please don't remove the posts by Mag's Tuning. At this stage at least I feel he is only helping solve a problem, not advertising.
That said, should we call you Maggie? :cool:
Mine I'm sure is a bit lower in RPM, otherwise very much the same. 40% throttle sounds about right, always the same RPM range (mine I'd say 2500-2600, then flares to close to 3000). Never happens under heavier throttle or lighter.
Lol Maggie is fine with us.
Can you post your video or a link to it? We are very intrigued by this flare and would like to see more of them to have a better understanding behind it.
Same as ours if the RPM or throttle % was under or over it never would flare. When we dove into it and noticed that it was only flaring at one spot is what lead us to believe that it was a pressure related issue with the TCM. Our questions are... Why is the flare only happening at one point in the upshift and why does GM have the TCM mapped like this? Going back to our 3rd dealer trip in when we were told that everything was doing just what GM designed and engineered it to do.....Why?
 

·
Super Moderator
Joined
·
20,120 Posts
speleos, please don't remove the posts by Mag's Tuning. At this stage at least I feel he is only helping solve a problem, not advertising.
...
Is it really a problem? Or, is it just something people don't like about the way GM's programmers work the torque management? Everyone should do some reading about trans programming from the earlier years (a good place to search is "May 8 trans flash" - or look at some of the early campaigns). Honestly, I've never been thrilled with the transmission programming, or the way TCC is used during run-up through the gears. I just learned to live with it.
 

·
Registered
Joined
·
909 Posts
Is it really a problem?...
Very good point, something I've been considering starting a new post about. Does this transmission flash ever, generally, sometimes lead to reliability problems down the road?
I would think it is a problem, as an engine jumping 300-500RPM between gears can't be easy on the torque converter/tranny, yes?
And when the mechanic drove mine he stated it was a problem. Add that they are supposedly pulling my transmission tomorrow morning, I would say my dealership seems to think it is a problem. But we'll see what they actually do.
I really don't know for sure though. Anyway, posting link I just uploaded to Vimeo...
Flash
 

·
Registered
Joined
·
2,636 Posts
Is it really a problem? Or, is it just something people don't like about the way GM's programmers work the torque management? Everyone should do some reading about trans programming from the earlier years (a good place to search is "May 8 trans flash" - or look at some of the early campaigns). Honestly, I've never been thrilled with the transmission programming, or the way TCC is used during run-up through the gears. I just learned to live with it.
I do not think it's a problem. I think a little flare is probably easier on the transmission then mucking with the software to create tighter, harsher shifts.
 

·
Super Moderator
Joined
·
20,120 Posts
I would think it is a problem, as an engine jumping 300-500RPM between gears can't be easy on the torque converter/tranny, yes?
I wouldn't think so. The torque converter is just a large flexible-vane hydraulic pump. When the TCC is unlocked, the pump has to regain pressure lost during lock-up. It's also this loss/gain of pressure in the converter which contributes to engine RPMs fluctuating on roads with changing gradients.
 

·
Registered
Joined
·
1,426 Posts
Very good point, something I've been considering starting a new post about. Does this transmission flash ever, generally, sometimes lead to reliability problems down the road?
I would think it is a problem, as an engine jumping 300-500RPM between gears can't be easy on the torque converter/tranny, yes?
And when the mechanic drove mine he stated it was a problem. Add that they are supposedly pulling my transmission tomorrow morning, I would say my dealership seems to think it is a problem. But we'll see what they actually do.
I really don't know for sure though. Anyway, posting link I just uploaded to Vimeo...
Flash
Thanks for the video ..
Based on the video .. . our 2019 Acadia SLT-1 FWD 3.6L V6 does not flare like that. . . so far at 3.000 miles on the odometer.
And that is about the throttle point and shift RPM I would normally drive at.
 

·
Registered
Joined
·
909 Posts
So why do some flare and not others? Should not all trannys behave similarly under similar driving conditions?
 

·
Registered
Joined
·
1,426 Posts
So why do some flare and not others? Should not all trannys behave similarly under similar driving conditions?
We would think and hope so. That said, these newer generation transmissions have a number of new " innovations" in them from what I've read.
For one, the Torque Converter Clutch (TCC) is not like the old "lock up" Torque Converter.

I've seen pictures of a 6 speed 6Txx tear down and the TCC actually has a clutch surface that can be variably engaged and allow slip under certain RPM and load conditions to provide smoother and less harsh shifts.
Whether this is what we are seeing or not is up for question or even related to the flare.

However, problems can arise when the TCC slips more than it should and then delay in engagement and other things can occur.
I've seen pictures of a torn down TCC in the 6 speed where the clutch material is somewhat burned and the mating metal surface is "blued" from heat due to slippage.

The bottom line I guess is .. how much slip and under what conditions is normal and is the TCC programming correct or affected by other operational conditions that then surface as shift flare, shudder, etc?
I can believe that more scrutiny in transmission programming could result in better transmission performance and reliability.
 

·
Super Moderator
Joined
·
20,120 Posts
So why do some flare and not others? Should not all trannys behave similarly under similar driving conditions?
Each one of us drives a vehicle differently. If drivers were robots, that might be more feasible.
 

·
Registered
Joined
·
909 Posts
Each one of us drives a vehicle differently. If drivers were robots, that might be more feasible.
Perhaps. But even JayTee2019 said he accelerates similarly. This is not a rare occurrence (daily). And the mechanic who drove it got the same flare a few times in a 5 minute trip. He came back and stated "wicked flare from 2-3 shift". So although I appreciate the reply, this is not about drivers, it's about the vehicle.
 
  • Like
Reactions: JayTee2019

·
Registered
Joined
·
909 Posts
I agree. I do not believe it is a very wide spread issue, not that I would even consider it an issue.
So nobody besides those who it's happening to considers it a concern?
In other words, if your car was doing this you'd ignore it? Your car daily surges like that and you wouldn't be concerned at all? Not questioning, looking for honest answers.
 
  • Like
Reactions: JayTee2019
81 - 100 of 184 Posts
Top