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Discussion Starter · #1 ·
I have a quirk that's popped up when towing my travel trailer.

When using the ERS and locking it to 4th gear on the 6T75, the transmission has started occasionally jumping into 5th on descents — when I don't want it to — and when I've supposedly barred it from using anything above 4. Even if I then manually set to 5, and try moving it back to 4, it will not downshift into 4, until I manually go all the way to 3, and then back into 4. It doesn't happen all the time, and I can't find a rhythm or reason as to when it will do this issue.

Is this the beginning of a potential transmission issue? Should I have the dealer reflash the software and see where that gets me first?

Any other thoughts or direction?
 

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A reflash can't hurt but IMO it's probably a deeper issue. I've owned two Acadia's and have never thought them to be the right tool for towing.

If I had a need to tow a travel trailer I would have a Silverado or F150.
 

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What good will wiping out the transmission's 'adaptive driving' programming do? It would be best to duplicate the situation while someone with a scan tool monitors transmission function.

You could buy one of those Class A RV's on that lot and tow the Acadia behind it. ;)
 

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Discussion Starter · #4 ·
What good will wiping out the transmission's 'adaptive driving' programming do? It would be best to duplicate the situation while someone with a scan tool monitors transmission function.

You could buy one of those Class A RV's on that lot and tow the Acadia behind it. ;)
Motorhomes don't really fit our lifestyle or needs — for the moment.

Tow mode should override the adaptive programming anyway, so that shouldn't be impacting the actual driving at this time. Not really too concerned with wiping out profiles on a 100,000 mile vehicle.

Trying to figure out why it would want to go into 5th gear. One would think if anything the vehicle would want to downshift into 3rd to maintain speed better and have more torque— unless I have a problem with a solenoid or some other problem with 4th.

I'm towing back today. I'll see if the issue repeats.
 

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What RPM would it be in 4th, maybe too high?
 

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... Not really too concerned with wiping out profiles on a 100,000 mile vehicle. ...
I would be. The transmission won't shift right because the vehicle thinks it's brand new again. May take a while for it to return to what's 'normal' for a high mileage vehicle.
 

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I'm towing back today. I'll see if the issue repeats.
Hire a ride-a-long transmission tech with a scan tool. They might enjoy the diversion from a normal work day. 🤣 🤣 🤣 (Would be a plus if you find one with cooking skill, too. LOL)
 

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Discussion Starter · #8 ·
What RPM would it be in 4th, maybe too high?
Runs at 3,500 RPM in 4th at 70 MPH. Not too high at all. The drivetrain is performing exactly as it has every other time, except for this one quirk.
 

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Discussion Starter · #9 ·
The drive back today exhibited the same behavior. Generally, I have the cruise set to 70 MPH on flats and rolling hills and use the ERS to put me into the gear I need for torque. Shift to 3rd to maintain speed up hills, cruise in 4th. It would never stay long enough in 5th, so I just starting locking that out last season.

If this is just silly electronic weirdness, I can learn to live with it — but it really is annoying having it shift into 5th without "authorization" on a downhill, not move back to 4th on command, and forcing me to shift into 3rd to override whatever the heck is going on, then finally back into 4th. It needlessly starts slowing my speed trying to stay in 5th coming out of the down slope, then I'm not in its preferred cruising gear in 4th, then I needlessly need to spike my RPM to 4,500 just to regain the velocity that was lost from it not downshifting fast enough.

This is the behavior that it exhibited in 'D' before I started using the ERS exclusively when towing. It's almost like the built in TCM parameters are taking over from the ERS...
 
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