2021 Tahoe HC Transmission failure @600miles

[Big Bad Allis]

Update: finally got the Tahoe back with 653 MI after their test drive. Service advisor gave us a warning before handing the keys over. He said that the one two shift is going to be really hard for a little while, until everything settles, and the trans "relearns" how to shift again. I found that a bit odd, so I asked him why. he stated because it's a brand new electronic valve body and the transmission was completely flushed of fluid and refilled with "better" fluid. He said he was told by the troubleshooters that it is normal. Not sure I completely agree with that because we got the car with 20 miles on it, and it ran just fine, until it didn't. [emoji2363]

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There will be some "relearning" but that is normal for most modern vehicles. The "learning" is based somewhat on the type of driving the driver does. It's a balance of driver input through the ECM and transmission control electronics. Not sure that technical names for all electronics involved. It will adjust the shift points. This should not really be noticeable in most cases.

I call BS on adding a "better Fluid". I would ask what the "better Fluid" is. As a lubricant engineer and owner of an oil analysis laboratory, I wold love to know what their idea of "better fluid" is.

 

[TAHOEpeful]

That is great news. Keep us posted on how it works out.

Thank you,Will do, hopefully all goes well!

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[TAHOEpeful]

No, you’re absolutely right. 100% of the time my gut and just generally “passing the smell” test has been more accurate than whatever reasoning the service advisers are going to feed you...

I would just continue to drive it as they have directed and probably wouldn’t be a bad idea to check your trans fluid levels every so many miles. If after a full tank of gas that 1-2 shift is still “hard”. It’d be taking it back...

Yes, definitely! I'm not a professional, but I'm also not a complete novice around anything motorized. I trust my instincts and intelligence more than I do any of the BS dealerships feed us. The Tahoe does shift ******* the one to two shift, almost feels like it's going to pull the front wheels lol. So far haven't smelled anything weird, wife just took it out to run some errands, I'll inspect it when she gets home. Thank you for the advice so far!

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[TAHOEpeful]

There will be some "relearning" but that is normal for most modern vehicles. The "learning" is based somewhat on the type of driving the driver does. It's a balance of driver input through the ECM and transmission control electronics. Not sure that technical names for all electronics involved. It will adjust the shift points. This should not really be noticeable in most cases.

I call BS on adding a "better Fluid". I would ask what the "better Fluid" is. As a lubricant engineer and owner of an oil analysis laboratory, I wold love to know what their idea of "better fluid" is.

I agree with you on the "relearning"for most vehicles, but what I don't understand is we got the Tahoe with 20 miles on it and it was shifting just fine. What I'm trying to say is was it programmed like that from the factory and didn't have to learn our driving habits, or was it trans already starting to slip from the gate? I'm torn on what to believe here. Although I wanted to test out the power of the 6.2, I couldn't because of the break-in period, but even driving normal it didn't shift hard like it does now.
To your point on the fluid, I chuckled when he said better fluid and then I forgot to ask what he meant, but I think I'm going to call back and ask what he meant by that. Thank you!

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[TAHOEpeful]

It was years ago but I have heard of a fresh trans or a rebuilt trans or even when a valve body is replaced, that there is a relearn process. IMO, that should be not happening now but what the hell do I know! I have heard the same thing when ECM had been replaced. The theory is that the relearn process is needed to help adapt to the way it is driven because different drivers drive differently. I have experienced that myself.

Thank you! You would think with today's modern technology this wouldn't be an issue and things would work as easy as we would want, but as you said what the hell do I/we know! [emoji2375]

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[OR VietVet]

I also agree with the "better fluid" comment. Now, he may have just meant that the fluid that was in there looked burned or had particles in it and they flushed it all out and now has better/new fluid. But if he meant something else, I would want to know what that meant or what he thinks it means. I would ask him and I would also want to see that on the work documentation. I would ask that if it is "better fluid", then why is it not documented on the paperwork? I am a stickler for details. I was very aware of what I told my customers when I was running shops and did not want to throw ******** comments at them. I wanted them to know the absolute truth of what I saw and what was done. Only one time in all my years of running shops did I tell a wild story. It was a customer that after 3 visits I knew he was WAYYYYYY to much effort to deal with. He called people names and said he knew we were going to rip him off..... I made up the wildest story and got him to leave. The owner of the shop came over and shook my hand and said thanks for getting rid of him.

 

[Big Bad Allis]

If they cannot prove they installed a GM approved fluid, GM can deny all future warranty claims. These transmissions are very particular. Also never install a multi-vehicle formulation either. They claim they meet OEM requirements but technically do not. Transmissions are very particular about viscosity, additives and friction modifiers.

 

[kristenlprice]

Not what I wanna hear!! I fought tooth and nail for a new transmission in my last Tahoe 2500 miles before the warranty went out. I’m so paranoid now about it. I hope I don’t have an issue in thus one . They literally called me a liar so many times on the last one, even after watching videos. Finally I called them to come get it at a football game bc I couldn’t back out. That was what finally got it after them keeping it several months off and on and nothing showing signs of any issues to them.

Bought end of July, drove lightly due to break in period. Wife was driving and it began revving high and cut power, slowed down,, and CEL came on. She was able to drive it home. We let it sit over night thinking it was a fluke. I hadn't experienced it so I tried the next day to drive it and it did the same thing to me. Took it home and tried to reverse in the driveway but got stuck in the middle of the street because reverse stopped working. had to drive it to the dealership because they weren't able to come pick it up that day and we were leaving for vacation. Dealer initially told us the transmission needed to be replaced! Needless to say my wife and I were EXTREMELY upset. A few days later, we were told it was a valve body in the trans and they ordered one from GM. When it FINALLY came, it apparently wouldn't program. [emoji2363] Waiting on new valve body and HOPING it works. Sorry for the wall of text, just had to vent!

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[Hrocks]

Bought end of July, drove lightly due to break in period. Wife was driving and it began revving high and cut power, slowed down,, and CEL came on. She was able to drive it home. We let it sit over night thinking it was a fluke. I hadn't experienced it so I tried the next day to drive it and it did the same thing to me. Took it home and tried to reverse in the driveway but got stuck in the middle of the street because reverse stopped working. had to drive it to the dealership because they weren't able to come pick it up that day and we were leaving for vacation. Dealer initially told us the transmission needed to be replaced! Needless to say my wife and I were EXTREMELY upset. A few days later, we were told it was a valve body in the trans and they ordered one from GM. When it FINALLY came, it apparently wouldn't program.

Waiting on new valve body and HOPING it works. Sorry for the wall of text, just had to vent!

Wow, this sounds like an “instant” replay of the 2KXX launch. Spending $70-$80,000 for a vehicle and having to be a first year guinea pig is beyond disgusting. I would keep returning to the dealer for the same exact problem to build a lemon law buy back case. Unfortunately, this has been a very common GM scenario.

 

[Dexmon]

Bought end of July, drove lightly due to break in period. Wife was driving and it began revving high and cut power, slowed down,, and CEL came on. She was able to drive it home. We let it sit over night thinking it was a fluke. I hadn't experienced it so I tried the next day to drive it and it did the same thing to me. Took it home and tried to reverse in the driveway but got stuck in the middle of the street because reverse stopped working. had to drive it to the dealership because they weren't able to come pick it up that day and we were leaving for vacation. Dealer initially told us the transmission needed to be replaced! Needless to say my wife and I were EXTREMELY upset. A few days later, we were told it was a valve body in the trans and they ordered one from GM. When it FINALLY came, it apparently wouldn't program. [emoji2363] Waiting on new valve body and HOPING it works. Sorry for the wall of text, just had to vent!

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I'm very sorry to hear that my friend. After what I went through with my 15 Suburban, I'm not buying one of these trucks until they work out the issues. The first two years of a redesign always have problems. I hope that's not a sign of more issues with your truck going forward.

 

[Rocket Man]

I agree with you on the "relearning"for most vehicles, but what I don't understand is we got the Tahoe with 20 miles on it and it was shifting just fine. What I'm trying to say is was it programmed like that from the factory and didn't have to learn our driving habits, or was it trans already starting to slip from the gate? I'm torn on what to believe here. Although I wanted to test out the power of the 6.2, I couldn't because of the break-in period, but even driving normal it didn't shift hard like it does now.
To your point on the fluid, I chuckled when he said better fluid and then I forgot to ask what he meant, but I think I'm going to call back and ask what he meant by that. Thank you!

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It’s possible that it since it initially learned when it had a bad valve body, it was adding line pressure to compensate and now it has a valve body that’s doing its job properly so the added line pressure is causing a hard shift until it re-learns if that makes sense. I know on the older (4l60 etc) transmissions there was supposedly a way to reset the adaptive learning but plenty of times this wasn’t done so when you got a new trans to replace a worn-out one it would shift weird for a bit. Hope things work out, you shouldn’t have to be going through this.

 

[tabraha]

Definitely will have to relearn but it usually doesn't take many miles for that to sort out (less than 50, more like 20). I had a Colorado with the 8sp issues and it went through a torque converter and had to relearn. Then it had to have the fluid swapped out for the better fluid to fight the shudder issues with the 8sp that it had originally. When GM changed spec to Mobil1 LV ATF HP it made the trans much better.

FWIW, I have the uprated version of the 10sp in my ZL1 and it is a beast. Probably the best auto trans I've ever seen in a vehicle. Crisp, fast and a helluva brain on it at the track.

 

[TAHOEpeful]

It’s possible that it since it initially learned when it had a bad valve body, it was adding line pressure to compensate and now it has a valve body that’s doing its job properly so the added line pressure is causing a hard shift until it re-learns if that makes sense. I know on the older (4l60 etc) transmissions there was supposedly a way to reset the adaptive learning but plenty of times this wasn’t done so when you got a new trans to replace a worn-out one it would shift weird for a bit. Hope things work out, you shouldn’t have to be going through this.

I never thought of it that way but it makes total sense that that's why it's shifting hard [emoji1417] thank you!!

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[TAHOEpeful]

Definitely will have to relearn but it usually doesn't take many miles for that to sort out (less than 50, more like 20). I had a Colorado with the 8sp issues and it went through a torque converter and had to relearn. Then it had to have the fluid swapped out for the better fluid to fight the shudder issues with the 8sp that it had originally. When GM changed spec to Mobil1 LV ATF HP it made the trans much better.

FWIW, I have the uprated version of the 10sp in my ZL1 and it is a beast. Probably the best auto trans I've ever seen in a vehicle. Crisp, fast and a helluva brain on it at the track.

Thank you, I wonder if that's what he meant with the "better" fluid comment, unfortunately or fortunately I've been too busy to call and ask or look at the paperwork. Can't imagine how awesome the trans is in your ZL1. Though,what I think you're suggesting to me is, that I run the Tahoe on the track to help it relearn faster right? [emoji23]/s

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[tabraha]

Now you're talkin!

But I'm also the same guy who took a 100 series Land Cruiser around the SC Highway Patrol training track...

 

[TAHOEpeful]

Update: hello everyone, sorry I haven't been updating on the regular or answering comments, we've been really busy with virtual schooling and other stuff. The trans is really starting to make an improvement with the shifting feel. The one to two shift is still a little rough, but nowhere near as hard shifting as it was. 2 to 3 still isn't as smooth as it was, or can be. 3 on up has made a big improvement where we barely even feel the shifts. We got it back with a 653 miles, and have maybe put 80 to 100 miles on it. Also a first world problem is, the new car smell is a little diminished because they had it parked in the shop for so long and it smells a little like the shop, but I digress. now that things are getting back to normal with it, I'm starting to fall back in love with the car. [emoji1417]

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[TAHOEpeful]

Now you're talkin!

But I'm also the same guy who took a 100 series Land Cruiser around the SC Highway Patrol training track...

[emoji23] oh man, what a feat and experience that must have been! New addition to the bucket list [emoji1419][emoji1605]

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[Fireman591]

Update: hello everyone, sorry I haven't been updating on the regular or answering comments, we've been really busy with virtual schooling and other stuff. The trans is really starting to make an improvement with the shifting feel. The one to two shift is still a little rough, but nowhere near as hard shifting as it was. 2 to 3 still isn't as smooth as it was, or can be. 3 on up has made a big improvement where we barely even feel the shifts. We got it back with a 653 miles, and have maybe put 80 to 100 miles on it. Also a first world problem is, the new car smell is a little diminished because they had it parked in the shop for so long and it smells a little like the shop, but I digress. now that things are getting back to normal with it, I'm starting to fall back in love with the car. [emoji1417]

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Great news!!!!!!!!

 

[TAHOEpeful]

I'm very sorry to hear that my friend. After what I went through with my 15 Suburban, I'm not buying one of these trucks until they work out the issues. The first two years of a redesign always have problems. I hope that's not a sign of more issues with your truck going forward.

Thank you and yes I agree with you about the redesign issues, but our 16 suburban was having trans issues so we I wanted to get rid of it before any catastrophic problems happened. I guess we should have taken that as a sign of things to come [emoji2363] but I'm hopeful nothing else goes wrong [emoji1693]

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[TAHOEpeful]

Yes it is totally disgusting for the amount of money we spent, never had these types of issues with other brands of cars that would he considered high-end such as Audi and BMW [emoji2375] I'm definitely going to keep a close eye on the trans going forward and if I feel the need to I will take it right back and start building a case, thank you for the advice!

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