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Transmission anxiety

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2020truck Enthusiast

2020truck

Posted
Posted

Hello.  I own a 2020 GMC Sierra high country 6.2l with 112k miles, bought used at 93k last year.  

 

I purchased the extended warranty, which really panned out.  I've used $17,000 worth of that warranty in ONE YEAR!

 

at 96k miles, whining from transmission.  Was caused by idler gear walking off the bearing within transmission.  Gear and pump replaced. 

 

At 110K oil pan leak.  Resealed.

 

At 112k, slight slip at low rpm slow speed.  Transmission replaced. 

 

I am very concerned about the quality of the transmission in this vehicle. It seems no matter how well they are cared for they will fail. 

 

Is there anyone with high miliage 10l80 out there?  If so what have you done?

 

Do you think this new transmission will have more longevity?  

 

I am seriously considering getting rid of this thing and buying a toyota.

I've owned bmws with less issues. 

 

What are your thoughts?  Thanks. 

 

 

newdude Senior Enthusiast

newdude

Posted
Posted

Well, the first one made it to 112,000mi.  No reason the new one shouldn't get to that if not much more.  

 

Early 10 speeds had the oil pump drive gear issue.  They don't "walk" so much as they'd develop play in them and if it was bad enough, start eating the gear teeth.  They updated that for 2022.  Any new or reman GM transmissions after that point have an updated gear.    The TSB - 22-NA-232 1..3

 

Otherwise, plenty that come to work with over 100,000mi that have never had work done aside from fluid changes.  

KARNUT Senior Enthusiast

KARNUT

Posted
Posted
On 4/20/2026 at 9:34 PM, 2020truck said:

Hello.  I own a 2020 GMC Sierra high country 6.2l with 112k miles, bought used at 93k last year.  

 

I purchased the extended warranty, which really panned out.  I've used $17,000 worth of that warranty in ONE YEAR!

 

at 96k miles, whining from transmission.  Was caused by idler gear walking off the bearing within transmission.  Gear and pump replaced. 

 

At 110K oil pan leak.  Resealed.

 

At 112k, slight slip at low rpm slow speed.  Transmission replaced. 

 

I am very concerned about the quality of the transmission in this vehicle. It seems no matter how well they are cared for they will fail. 

 

Is there anyone with high miliage 10l80 out there?  If so what have you done?

 

Do you think this new transmission will have more longevity?  

 

I am seriously considering getting rid of this thing and buying a toyota.

I've owned bmws with less issues. 

 

What are your thoughts?  Thanks. 

 

 

I’d be more concerned with the 6.2. 2020 seems to be when their problems started.

2020truck Enthusiast

2020truck

Posted
  • Author
Posted (edited)
On 4/25/2026 at 7:32 AM, KARNUT said:

I’d be more concerned with the 6.2. 2020 seems to be when their problems started.

Best I can figure, the issue centers around bad bearings, and over chamfered oil holes on the crank. Along with poor crank finish.  If my truck had an engine problem it would have manifested itself by now.  When the pan was removed the dealer checked for heat signs.  There were none.  On Top of that the oil has been changed religiously at 5000mi.   If anything was going to happen, it would have. 

 

But your comment highlights another one of my concerns. 

Edited by 2020truck
  • Like 1
2020truck Enthusiast

2020truck

Posted
  • Author
Posted
On 4/25/2026 at 7:27 AM, newdude said:

Well, the first one made it to 112,000mi.  No reason the new one shouldn't get to that if not much more.  

 

Early 10 speeds had the oil pump drive gear issue.  They don't "walk" so much as they'd develop play in them and if it was bad enough, start eating the gear teeth.  They updated that for 2022.  Any new or reman GM transmissions after that point have an updated gear.    The TSB - 22-NA-232 1..3

 

Otherwise, plenty that come to work with over 100,000mi that have never had work done aside from fluid changes.  

Yes, I saw this first hand.  

The bill to repair a bad idler gear and pump is $4600 at a dealer. 

 

I am wondering if the latest valve body is really better than the original.  These transmissions are not cheap. 

 

Do yiu know of any high miliage transmissions with the updated vb?   I think it's fairly new. 

  • 2 weeks later...
Jerry455 Enthusiast

Jerry455

Posted
Posted

I bought a used 2021 Suburban 6.2 HC in May of 2024 with 70,000 miles. I had to put in a new trans at 80,000. I don't know the maintenance done but after using the Dexron ULV, I am going to be replacing fluid at least every other year. You have to shake it before using it. It is like pink water. I am not very confident in its long term use. I think the additives wear out. I am going to be installing a larger pan with a drain plug. Next Gen transmission has some interesting articles.

2020truck Enthusiast

2020truck

Posted
  • Author
Posted (edited)
On 5/11/2026 at 12:04 PM, Jerry455 said:

I bought a used 2021 Suburban 6.2 HC in May of 2024 with 70,000 miles. I had to put in a new trans at 80,000. I don't know the maintenance done but after using the Dexron ULV, I am going to be replacing fluid at least every other year. You have to shake it before using it. It is like pink water. I am not very confident in its long term use. I think the additives wear out. I am going to be installing a larger pan with a drain plug. Next Gen transmission has some interesting articles.

I think the 24 still had the old bad VB.  Also, from what I've heard the mobile 1 ulv is better than ac delco.  Yea its a real shame on GM for what they have done. 

 

The 21 had thr bad vb and bad idler 

Edited by 2020truck
newdude Senior Enthusiast

newdude

Posted
Posted
2 hours ago, Jerry455 said:

I would be surprised if AC Delco ULV is not a Mobil fluid.

 

 

Its not.

 

Phillips 66 Lubricants makes it.  

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