2020 8-speed transmission shudder

JFDNH · March 7, 2021

I have a 2020 Silverado Custom 2.7 turbo with the 8-speed tranny. There is a serious shudder between 35 and 55 that drives me crazy. I know this was an issue for 2019 models but it was supposedly fixed by the trans flush/replacement with the new Mobil 1 fluid. Does anyone else have this issue with a 2020 model? I need to take it to the dealer for a seat belt recall anyway and just wanted some more info on the tranny issue before I do.

Thanks.

Dunn · March 8, 2021

unless your sure its coming from there idk if thats the tranny.....most of tranny issues were between 1st and 2nd gear (clunk or slam)....my RST had it but wasnt bad at all and rarely happened.....my 21 gmc has been flawless

maybe its tires, balance or driveshaft vibration......

there are some huge threads on this though

Edited March 8, 2021 by Dunn

JFDNH · March 8, 2021

No doubt it's trans, if I manually shift, the shudder goes away completely. The shudder is absolutely a common issue with the 2019's, there is a service bulletin on it. I'm wondering if I got an old trans when mine was built. My wife has a 2020 Buick with the same issue and her 2017 did it as well. It doesn't bother her but I hate it.

2024Denali · March 8, 2021

4 hours ago, JFDNH said:

No doubt it's trans, if I manually shift, the shudder goes away completely. The shudder is absolutely a common issue with the 2019's, there is a service bulletin on it. I'm wondering if I got an old trans when mine was built. My wife has a 2020 Buick with the same issue and her 2017 did it as well. It doesn't bother her but I hate it.

Definitely the tranny. I once caught a tech talking about the shudder and how they couldn’t really do much about it when he test drove it (dash cam audio). But they did do an update and swapped the oil and it fixed 80% of it. Doesn’t really bother me as much.

bigdoug42 · March 9, 2021

I had this issue at about 10000 miles on my 2019 LT Z71, sounded like I was running over rumble strips at times, dealer flush and replacement with updated trans fluid fixed it completely. They have a scope that can diagnose the shudder while driving.

Chevrolet1 · March 18, 2021

Here's my input and hopefully it helps. Right after purchasing my CPO 2019 LTZ, I had two symptoms. One was that it felt I was being bumped from behind when I stopped (i.e. hard downshift to first). The second was what felt like rapid shifting twice from one gear to the next, and it would sometimes lunge and buck when shifting.

My local dealer did the trans control module update for the first symptom, and that issue is completely gone.

They performed a fluid change for the second symptom under TSB 19-NA-121 (torque converter shudder). Shifting has dramatically improved and I don't feel any shifting issues so far. They said to wait 200 miles for it to be completely addressed.

Update: Ever since I had the trans control module reprogrammed, I've been getting better gas mileage. With my mix of city / hwy driving, my average was previously 18.8. After a few weeks of driving it after this reprogram, I'm consistently getting 19.3 under the same driving conditions.

Edited March 20, 2021 by Chevrolet1
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