My ZR2 Colorado the transmission was shuttered hard. I just brought it in yesterday they flushed the transmission and replaced it with an upgraded oil. It’s seems to be working well for now. It’s only been one day. We’ll see. I’m reading nightmare stories of the Colorado having this problem.
That could be the least of your problems down the road. I have a 2018 ZR2 and the transmission was shaking and stuttering at10K miles. I just took it in yesterday and they flushed the transmission then replaced the gear oil with updated/better oil for that trans. It’s been one day and so far it’s working good. FYI