I took my 2021 Silverado to the dealership at about 2500 miles with a slight shudder when decelerating and accelerating. It feels like it’s riding on rough pavement all the time, that’s the only way I can describe it. The dealer did a reset on the engine computer but it didn’t fix the problem. The first time I had to go back to the dealership and ride with the service manager to duplicate the problem, and after the engine reset they said the problem was resolved. It’s not. I’m at 5000 miles at this point. It’s hard to tell where this is coming from. Any issues with the 2021’s that have these symptoms?

 

My 2021 Silverado, 5.3, 8 speed has intermittent rough downshifts into 1st gear. I have left it at the dealer twice for half days to trouble shoot, they cant find out why it does it. They want me to leave it for two or three days, but don't have a loaner car available, because of the chip shortage. They say I will just have to just wait. GM has not released any information on this issue on 2020 or 2021 vehicles to my knowledge.

 

My post from April ...

8 Spd
My 17 Silverado 8 Spd was connected to a 6.2. Yes hard shift knock between 1st and 2nd was always there. Yes, converter starting to fail. Extreme slippage under load and higher trans temps. GM suggested flush and refill with new type fluid performed under warranty, which did nothing to fix problem. A contact I was introduced to via a friend who is associated with GM said get rid of it, Nothing GM will do can fix it 100%. My trans was slipping very bad, would not hold set cruise speed on hills, I had to engage manual shifting to get trans to downshift in order to maintain set speed on hills.

I trade up to a 20 Silverado 6.2 with 10 Spd. No more issues. My thought is GM does not want to fix issue, so you will purchase a new truck like I did. Yes, I dont like their approach and dealers seem to be caught in the middle.

 

I’ve had that mindset too where I don’t think they’ll fix it at all. Problem is I’ve never owned a Chevy before this and unless it gets resolved, I likely won’t buy another one. I hate that because I think these Silverado’s are the best looking truck on the road.

 

So far, with only about 5800 miles on it, the 10 speed has been great..

 

Spoke to a friend today with the 10 speed in his Sierra and said good things about it too. I may consider that transmission in a Silverado when it comes time to trade it.

 

I have a 22 custom 2.7 and I too felt the feel a light vibration under light throttle. I brought to the dealer and had the trans oil changed and it did nothing. All diagnostics are normal. I even had a gm engineer check it after going to the dealership several times.

I read it could be the torque converter, but on mine, my rpms don’t jump and my diagnostics are fine.

I read a bulletin from like 2012 about the AFM cylinder shut off. Granted it is for the 6 and 8 cylinders, but I read that the AFM can cause a vibration in the steering wheel, seats and pedals. It is Normal apparently and no fix for it. It has something to do with exhaust tones or something along those lines.

anyway I read you can disable AFM by either manual mode in L5 on a 6 speed truck or getting the AFM module to bypass the AFM. I have an 8 speed truck so I tried L7 and the vibration is gone. I believe L8 still uses AFM. The AFM shuts off cylinders 2 and 3 in the right conditions.

I did some more digging and the AFM is discontinued for 2022 and it is DFM now, however the 2.7 still has AFM. I am not sure if there is a module to bypass AFM on the 2.7t, but L7 seems to work for me.

anybody have similar issues with this?

 

I joined the board to comment on our 2019 Silverado Trail Boss 5.3L Ecotec3 V8 transmission. 33,000 miles. Noticed on the way home from Cleveland to Toledo area a couple weeks ago the transmission feel like it was slipping. 1st to 2nd or any other gears. Took it to the dealership for a $139.95 transmission diagnostics. Was told they found nothing. I asked if the tech drove it more than just around the building...told them we filled it up before we dropped it off and to take it for a 20-25 minute drive. They said they did that. They still did not find anything. We were told "the engines have changed since 2016 (our last Silverado) and that there is no hydraulic softeners n it so when the fluid builds up, there is no cushion when shifting so it "bangs" into gear." Um, what?
We were then told to "bring it out immediately when it does it again and we won't need an appointment." Okay - but I have to pay another $139.95 for a diagnostic! The tech said "at least it will be documented so if something is wrong with the transmission, we'd have a leg to stand on."
I'm so upset. We felt it again today just driving to and from lunch.
We've had Silverado's for 30+ years. This may be our last. Not sure if any of you all had your engine oil cooler lines leak and detach from the crimp joints. Had that happen in March this year. Lost all the oil on the road. Found out there was a "customer satisfaction program" to address that. Thanks for the snail mail letter or email. Nope...find out on your own while you are driving down the road and you lose oil pressure and start smelling oil burning and look out your mirrors to see a trail of oil behind you. Thank goodness we weren't pulling our 32' travel trailer.

 

I’ve had some sort of vibration which I self diagnosed as the AFM vibrating on the 2.7t engine. Now I have a new issue that happened once- when I was braking the truck shook pretty aggressively, felt like a manual trans being left in gear when you’re coming to a stop.

anyone have this happen? Happened once in 4000 miles on my truck. Dealer told me it’s probably “drivetrain lash” and it’s “normal”. Huh???

 

I purchased my 22 custom with 2.7 in august. First 1000 miles it was great.

Now 2500 miles, I feel like the truck is vibrating and a lot. Can never feel the exact same vibration, but it’s there. Until reading the above user putting it in manual mode, L7, the vibration completely disappeared.

Now I looked into this afm and have found this to probably be the culprit. The transmission is great, no complaints. It was just the vibration while driving. There has to be a way to permanently turn it off. Read about some sort of tuning. But have no idea where or who to talk to about getting this done.