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Discussion Starter #1
Recently I have noticed that when driving my 2017 Acadia at slow speeds when shifting from 2-3 (need to double check if its from 1-2 or 2-3) it seems it holds RPM for a bit too long before shifting to the next gear.
This is probably more pronounced during slow speeds as vehicle is going smoothly and holding RPMs high is easily detectable at this speed.
Wanted to know if this is expected behaviour of 6T75 transmission or something is wrong?

If Denali displayed the current gear in DIC, it would have been more easy to know which shift. Plus for few its fun to know shift patterns. ;D
 

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I haven't noticed that happening with mine. Maybe your easier on the gas peddle than I am. What I
have noticed is it won't take a full throttle take off when its in the 2WD mode. The traction control picks up a possible wheel slip and stops you acceleration. 3/4 throttle is fine but not full throttle. If you want a full throttle take off you need to switch to the AWD mode, it will jump like a rabbit and go as long as you stay in it in AWD.
 

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is this the new Acadia- or the old body style?


But, you can try to gently accelerate for a bit and let off--
or
let off the gas-

one of these 2 usually will cause a shift.

thats what I do with my 2010 when its at that point where conditions are 'right' or 'wrong'-- whichever way you want to look at it.... where it wont shift--- but you want it to.
I believe its a gentle acceleration- and then let off-- and it shifts.... sort of help it decide---.
 

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rbarrios said:
is this the new Acadia- or the old body style?


But, you can try to gently accelerate for a bit and let off--
or
let off the gas-

one of these 2 usually will cause a shift.

thats what I do with my 2010 when its at that point where conditions are 'right' or 'wrong'-- whichever way you want to look at it.... where it wont shift--- but you want it to.
I believe its a gentle acceleration- and then let off-- and it shifts.... sort of help it decide---.
I catch myself doing that in some cars I drive and also in my Traverse at times like a normal reaction.
 

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Discussion Starter #5
rbarrios said:
is this the new Acadia- or the old body style?
This is the 2017 Acadia

rbarrios said:
But, you can try to gently accelerate for a bit and let off--
or
let off the gas-
one of these 2 usually will cause a shift.
Yes, this usually works. But if you are in situations like entering a yield trying to merge into another road, then in such scenarios its not convenient to do all these tricks(rather you don't want to let off gas). And you basically end-up getting that jerk feeling when gear shifts from (while at high RPM) to upper gear (which also gives that freewheeling feeling).


If we look at GM spec for 6t75 (http://gmauthority.com/blog/gm/gm-transmissions/m7x/#tab-2) it says "The first-to-second upshift, however, is a freewheeling action, where the second gear clutch engages while the first gear one-way clutch spins freely. This allows a greater degree of smoothness at lower vehicle speeds." Not sure if this has something to do with what we are talking here.
 

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go-denali: did you ever get resolution to this? I've been experiencing the same thing on my 2017 Denali. It often hesitates when shifting from 2nd to 3rd (and occasionally from 1st to 2nd), especially at lower RPMs. It doesn't appear to occur at higher RPMs or if I control the shifting manually. I've taken it to my dealer and they report "working as designed". I'm still not sure.
 

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jonwd said:
go-denali: did you ever get resolution to this? I've been experiencing the same thing on my 2017 Denali. It often hesitates when shifting from 2nd to 3rd (and occasionally from 1st to 2nd), especially at lower RPMs. It doesn't appear to occur at higher RPMs or if I control the shifting manually. I've taken it to my dealer and they report "working as designed". I'm still not sure.
Might try putting it in AWD or sport mode and see if it does the same thing. The traction control feature might be picking up a potential wheel slip if its in 2WD
 

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One thing GM is doing across the board...an ignition retard just before an upshift. This makes things easier on the transmission clutches. All three of my GM cars exhibit this...sometimes annoying and sometimes not so much.
 

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Discussion Starter #10
jonwd said:
go-denali: did you ever get resolution to this? I've been experiencing the same thing on my 2017 Denali. It often hesitates when shifting from 2nd to 3rd (and occasionally from 1st to 2nd), especially at lower RPMs. It doesn't appear to occur at higher RPMs or if I control the shifting manually. I've taken it to my dealer and they report "working as designed". I'm still not sure.
No I haven't gotten any resolution on this. From what I have seen this happens in either FWD, AWD, didn't get chance to reproduce this in other modes.
Similar to your observations, this doesn't seem to happen at higher Speeds or RPMs.

I had raised this concern with my dealer and they said their technician drove it and didn't find any issues.
This was hard to repro while I was driving with technician in the back and usually such things only driver will feel.
But when I was talking with him, he said there is lot of computer magic going on behind-the-scenes that could cause this or something to do with how torque converter clutch was engaged by computer.
He also suggested using high octane fuel to see if that will resolve this problem. I had tried high octane fuel for two full tanks at one time to see if I get more power, high mileage, but don't remember if issue exhibited during those runs.

Personally I am thinking if the shifts of this transmission are adaptive (like eg MDX) it could be some bug in the shift logic that got introduced in 2017 Acadia.
Also hopefully its nothing to do with any transmission part being damaged or worn out too quickly.

jonwd,
What type of Acadia trim is yours? Trying to see if this is somehow only seen on Denali's or other models too.
 

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go-denali said:
This is the 2017 Acadia
Yes, this usually works. But if you are in situations like entering a yield trying to merge into another road, then in such scenarios its not convenient to do all these tricks(rather you don't want to let off gas). And you basically end-up getting that jerk feeling when gear shifts from (while at high RPM) to upper gear (which also gives that freewheeling feeling).


If we look at GM spec for 6t75 (http://gmauthority.com/blog/gm/gm-transmissions/m7x/#tab-2) it says "The first-to-second upshift, however, is a freewheeling action, where the second gear clutch engages while the first gear one-way clutch spins freely. This allows a greater degree of smoothness at lower vehicle speeds." Not sure if this has something to do with what we are talking here.
Yes, it is understood that it is a 2017. But which type of Acadia. The new, reworded vehicle or the same old vehicle which was produced in 2016?
 

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go-denali: your experience so far sounds very similar to mine. I have the (new) 2017 Denli trim. Anyone else experiencing this or have any insight?
The strangest part to me is that it's so specific to the shift from 2nd to 3rd. What's so special about that?
 

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We've got the FWD Denali with the wife being the only driver, no way is she going to notice anything unless it's really noticeable. Our son has driven it Charlotte< NC about 150 miles on I-85 during rush hour traffic with some stop and go and he didn't notice anything and he would have said something.
 

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jonwd said:
...
The strangest part to me is that it's so specific to the shift from 2nd to 3rd. What's so special about that?
Maybe it's because 2nd-3rd is the range where most acceleration takes place in normal urban, or suburban driving. I always thought the transmission shifted out of 1st a bit too soon. :shrug:
 

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Our 2017 Denali is experiencing the same issue. It doesn't do it all of the time so I haven't taken it to the dealer yet. I haven't noticed what drive mode I am in when it happens. My wife noticed it and mentioned it to me. I had experienced it prior to her saying something but its not my daily driver so I try not to bring up things to her unless they are major...

Its almost like the transmissions is slow to shift into third gear. I was hoping it would learn our driving patterns and change that hasn't happened yet...

For those that have experienced this how often does it happen?
 

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Discussion Starter #16
DenaliGuy said:
Its almost like the transmissions is slow to shift into third gear. I was hoping it would learn our driving patterns and change that hasn't happened yet...
Yup, I too get this similar feeling that transmission has shifted out from 2nd , goes in neutral and has yet to engage into 3rd.
Please let us know what your dealer has to say about this, mine didn't take it seriously.

DenaliGuy said:
For those that have experienced this how often does it happen?
This happens very often for me, when I am driving at slow speeds. Typically this is very easy to reproduce by (1) Come to a full-stop at red signal (2) On green, start accelerating very slowly and pay attention to how 2-3 shift gives that feeling of transmission going into neutral between shifts 2-3.

Also I am at 6K+ miles already. May be this starts showing up prominently after certain miles? :shrug:
 

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go-denali said:
Yup, I too get this similar feeling that transmission has shifted out from 2nd , goes in neutral and has yet to engage into 3rd.
Please let us know what your dealer has to say about this, mine didn't take it seriously.
This happens very often for me, when I am driving at slow speeds. Typically this is very easy to reproduce by (1) Come to a full-stop at red signal (2) On green, start accelerating very slowly and pay attention to how 2-3 shift gives that feeling of transmission going into neutral between shifts 2-3.

Also I am at 6K+ miles already. May be this starts showing up prominently after certain miles? :shrug:
We are at 6K+ as well. We usually drive it in 2WD but with the snow we have been getting it is in AWD mode now. I have to see if it makes a difference next time. Prob won't take it in unless it gets worse or if the wife keeps saying something about it.
My wife also mentioned it feels slower in AWD vs. 2WD mode. I can't confirm that one either....
 

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Discussion Starter #18
I don't have detailed knowledge, but from what I could understand from information available on internet.......could this problem be related to how torque converter clutch is operating?
Seems like (for most vehicles) torque converter clutch usually engages when you go into 3rd (or 4th) gear. So this issue could infact be related to the TC clutch operation and not with gear shifts themselves ?
Just wanted to know what other folks think about this.
Since 6TXX transmission has been in use for so long, wondering if there is any history of TC Clutch issue for this tranny?

At 8k+ miles, I still experience this at slow speeds. :(
 

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Still experiencing it here too - about 7k miles. One additional piece of information I've recently discovered: it's FAR more likely to occur if I have just spent a significant time coasting. For example, coast from expressway speeds off an exit ramp, all the way to a stop. When I take off again it will pause shifting from 2-3 virtually every time.

It doesn't appear to make a difference whether I coast in Drive or Neutral, though the longer the coast, the more severe the hiccup.

Anyone else experiencing the same?
 

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go-denali said:
Recently I have noticed that when driving my 2017 Acadia at slow speeds when shifting from 2-3 (need to double check if its from 1-2 or 2-3) it seems it holds RPM for a bit too long before shifting to the next gear.
This is probably more pronounced during slow speeds as vehicle is going smoothly and holding RPMs high is easily detectable at this speed.
Wanted to know if this is expected behaviour of 6T75 transmission or something is wrong?

If Denali displayed the current gear in DIC, it would have been more easy to know which shift. Plus for few its fun to know shift patterns. ;D
It would help to have a definition of "a bit too long" and to know the actual RPM's you are seeing.

George
 
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