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9-speed Transmission Issue?

16K views 25 replies 14 participants last post by  jsimmons0166 
#1 ·
We just brought home a 2021 Acadia Denali and have had two instances where it has had trouble shifting into gear. Feels like a bad transmission slip that gets to the point that I can't even drive it out of my driveway now (car is in drive, engine revs like it is in neutral).

I was able to get it drivable again the first time it happened by switching it in and out of tow/haul mode as that seemed to force it to pick up a low gear. The dealer couldn't reproduce it and just reprogrammed some software per a GM bulletin, but the issue re-occurred a day later. I didn't use the tow/haul 'trick' to force it back into gear so the dealer can experience the issue.

Since this is a new model, I was curious if any other '21 owners had any transmission issues to report. It is possible I just got a lemon that was put together late on a Friday afternoon...
 
#2 ·
Could this simply be driver error in use of the push-button shift? :unsure:
 
#4 ·
You'll probably have to show the error to someone at your service center before they can figure out if there's any problem.
 
#5 ·
It has been there twice now. The first time the error code was analyzed, and software 'reset' per service bulletin. Not looking for a solution, just curious if anyone else with a '21 has had issues. I'm going to take another one home with me to see if it has the same problem.

Thanks!
 
#6 ·
I just turned 1000 miles on my 21 Denali and havent noticed any transmission issues at all. The shifting is seamless and Im really happy with it.
 
#12 ·
And loads of them headed to other GM plants/parts distribution warehouses. ;)
 
#17 ·
The shop told me that too much grease was used in the assembly of some transmissions in the 2021 Acadias. First they re-learned the transmission and made me drive it another 500 miles. Then they flushed the transmission fluids and made me drive it another 200 miles. They said about half the time, the flushing fixes the issue. Unfortunately it didn't fix the issue for me. So they're ordering a new transmission. I'm waiting a week to follow up and see when I can expect the new transmission. If the answer will put me outside the coverage time of lemon laws, I'm taking this thing back to the dealership and making them buy it back.
 
#19 ·
No lights or codes. I was able to take it in without any kind of breakdown. GM is aware they sent out faulty transmissions so I would definitely make an appointment over any strange transmission behavior. I believe they're in the middle of a class action lawsuit over their 2015-2019 transmissions, so it's in their best interest to check everything out.
 
#23 ·
I wanted to add to this forum that we too are having issues with our 2021 acadia denali transmission. 6k miles and started at 500 miles. In the morning is when the shudder is really bad between 1-2 and 2-3 gears and have had issues when slowing down the transmission shifting hard. Took it in two times now, first time they said computer didn't download anything so no issues. Second time they said there is a bulletin to flush the transmission so they flushed it still said no codes were noted. We are taking it back in a third time because after the flush it is almost undeliverable.
 
#25 ·
We just brought home a 2021 Acadia Denali and have had two instances where it has had trouble shifting into gear. Feels like a bad transmission slip that gets to the point that I can't even drive it out of my driveway now (car is in drive, engine revs like it is in neutral). I was able to get it drivable again the first time it happened by switching it in and out of tow/haul mode as that seemed to force it to pick up a low gear. The dealer couldn't reproduce it and just reprogrammed some software per a GM bulletin, but the issue re-occurred a day later. I didn't use the tow/haul 'trick' to force it back into gear so the dealer can experience the issue. Since this is a new model, I was curious if any other '21 owners had any transmission issues to report. It is possible I just got a lemon that was put together late on a Friday afternoon...
24,000 miles and mine just started this until it gets up to 20 mph
 
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