I need some advice

GMC303SNET · September 27, 2020

I'm sorry this is so long. I've got a 2020 Sierrra SLT 2WD Super Crew. Bought it brand new in January 2020. At 400 or so miles the following problem started: When driving normally and coming to a stop there was out of nowhere a sudden jerk between second and first, usually around 3 MPH. This went on for a couple of days and went away. Since then it's done it maybe a dozen times so the problem is intermittent. I took it to the dealership after the first incident and they reprogrammed the module which controls my 8 speed transmission. The problem came back a few weeks later. By the time I was able to get to the dealership again it stopped. This problem can last anywhere from a couple of days to the next time I shut it off...just depends - no rhyme or reason. After numerous discussions with the dealer, they said bring it directly here when it does it again. Finally, I was able to get it there last week. They didn't want to take it. They said they had no loaner car and asked that I come back the next week. I was able to have the service rep ride with me and feel what the problem was. He stated this was a new problem to him but he definitely could tell something was wrong. I did bring the truck back per their request, however, it was running fine with no jerk so this time I was informed that there was nothing they could do. This past Saturday it started it again and I drove right to the dealership. They again reprogrammed the module. They did not give me service ticket showing what was done. I was more or less dismissed and informed that I need to drive 500 to 800 miles for the adaptive transmission to 'learn' my driving methods. I'm tired of having to deal with this and I'm thinking of filing a lemon law notice since they can't/won't fix it. Anyone have any ideas as to what this is, and or what I should do? I need to add that the jerking motion is always on the downshift between second and first around 3 MPH when the problem does occur. It runs smooth when the problem is not present.

Edited September 27, 2020 by GMC303SNET

batman900 · September 28, 2020

It's a common 8 speed transmission complaint (among many). The only thing that smoothed mine out was slowing down more gently (slower) than I normally would right before the 2-1 downshift to prevent the clunk/jerk. Sometimes its just random without a rhyme or reason. I don't think you will find a fix for it.