2020 At4 Transmission problems

[Supercup]

17 hours ago, bamorris2 said:

The new 10 speeds are junk. Stick with tried and true 8 speed.

 

I would say that it was tried and discontinued.  Most 8 speeds worked just fine, just like the 10 speeds.  The 10 speed is a better platform with newest engineering - mine is fantastic - but one man's junk is another man's treasure! 

[Supercup]

17 hours ago, bamorris2 said:

The new 10 speeds are junk. Stick with tried and true 8 speed.

Tried and True 8 speed was "discontinued " after a few short years  - 10 speeds are latest and greatest - time will tell - but mine has been great.

 

One man's junk is another man's treasure! 

[Ltz73]

My 8 speed in my 2018 Sierra was total garbage. After numerous attempts by dealer to resolve all the issues even they gave up and started with the “can’t replicate it” and “that is normal” BS. I finally threw in the towel and got a 2020 with the 10 speed.  Best move I ever made, it is a dream! Smooth quick shifts no clunking, jerking, slipping torque converter. Getting rid of the 8 speed transmission is long over due by GM if you ask me. 

[Lee dillard]

So my 2020 150p ltz with 3.0 and tenspeed broke down 30 days ago with 13000 miles on it code said trans module put a new one in threw the same code replace wiring harness between ecm and module threw same code then said to replace ecm threw same code now rhe engineer want to string wires like rewiring a 1992 hewes bonefisher flats boat filed a lemon law today 

[Marco TX]

Have a 2020 AT4 Diesel, and the transmission is already out.  Waiting on dealership to repair.  Told me that they had 2 transmissions in front of it.

 

 

[Crozet]

2020 GMC Sierra 1500 AT4 3.0L Duramax
 

So, I have 39k miles on this bad boy. I love the truck but have had major problems. 
 

Check engine light come on the first time. Codes for transmission. Took back to the dealer, said they it was fine. Engine light went off there- 15k miles. 

 

22k miles light came back on, took it in, same thing. 
 

28 k miles light came of, went off later that day. Fast forward, came off the highway at 39k, you could hear something break. Limped home, clunking the whole way. Towed to the GMC dealer- transmission shot.
 

GMC replaced the transmission as of yesterday- 8/26/22.

 

driving home, check engine light back on. I haven’t checked the code yet but let’s just say I’m pissed.  

[MyDefectiveGMC]

So love my AT4 3L diesel but since April had nothing but trouble with the transmission. They flew in a GM engineer. He said it was a module. It finally came in. Changed it out. Didn't go 10 miles down the road before it started doing the same thing. Now they've changed out the transmission. Didn't even take it for a test drive after replacing it very next morning had the same problems.. now they're telling me they're supposedly an update coming out in October that will fix it. Meanwhile I have 50K plus vehicle that is practically undrivable. 

[Grover67]

What was your transmission doing that was causing you problems?

 

-Grover67

[Greyhound6.2]

I have a 6.2 with the 10 speed and developed a gear whine, it has run fine no CEL and shifts fine no problems just high pitched whine, dealer wants to put a new transmission in it waiting to hear back tomorrow on timeframe. how long have you guys had to wait to get a new transmission? 

 

[ajs800]

My 2020(5.3) at4 10spd started acting up around 14k miles and was replaced 2wks ago at 38k miles.   I have zero confidence in the new one. 

Edited September 17, 2022 by ajs800

[Tammy N]

We have a 2020 GMC 1500 sierra 5.3l 10sp

elevation pkg. 2nd owner. We bought extended warranty… highest one we could get with dealer 50k. We have had for 1 1/2 years. Reached 135k friday. Previous week shutter started. Dealer said needs new one @$6k because we aee out of warranty.

i have been researching today and finding all kinds of problems notes on 10sp, tgat gm knows about.

we don’t have back up vehicle and we don’t have $6 k to fix. I am in process of getting with the service manager… then i will keep moving up the “chain” until i get results of them backing theor product and replacing no cost. If that doesnt work… looking at lawsuit! Is tgere a class action on the 10sp?

[theAT4]

2020 at4,122k , 5.3 10 speed

hey i Have this truck since cero miles most miles on hwy I've been with this shudder about 5 months , now.. this kind of issue is common on GMC  trannies , at the moment I really dont know how to proceed is my only vehicle.

but sometimes it feels like is grinding something with tires , sometimes is pulling back and so on , some people says AMZOIL does a fix but who knows . the only thig that I can think of class action law suit because historie of this companie says they been seeling this vehicles knowing this issues

[2016 Sierra Owner]

8 hours ago, theAT4 said:

2020 at4,122k , 5.3 10 speed

hey i Have this truck since cero miles most miles on hwy I've been with this shudder about 5 months , now.. this kind of issue is common on GMC  trannies , at the moment I really dont know how to proceed is my only vehicle.

but sometimes it feels like is grinding something with tires , sometimes is pulling back and so on , some people says AMZOIL does a fix but who knows . the only thig that I can think of class action law suit because historie of this companie says they been seeling this vehicles knowing this issues

There are a few class action law suites already against GM for the 8 speed transmission issues. I don't think any have gotten resolved so I wouldn't hold your breath or wait for that outcome.