Found this on youtube comments on this vid
Has anyone tried this to stop or lessen the shake?
Comment from video
I took mine in twice for it. The first time they said it was normal too. I didn't buy it, so i took it in the second time . They kept my truck for like 5 days. Finally they called gm. They said to shim the right engine mount 2 most inner bolts 3mm. They did this and it work! I can't hardly feel any vibration at all. There is some, but not really noticeable, so I am happy. I don't know if you watched it or not, but I have another video on here labeled "vibration on a 2014 Chevy silverado" that shows the vibration I was having.