Hey Guys here is the story! Last summer at the 4500 KM mark I had a vibration that started in the exhaust manifold are off and on then constant at the 1500 RPM mark. I brought it to the dealer and they retightened the bolt that holds the prop shaft. It was good for a week then it came back and the next visit they put lock tight on it. Good for another week and it came back so on the third visit the replaced the bold and again it lasted a week. So there is an issuer with 2016 and 2017 C7's that we are putting high mileage on according to GM but it's not happening on the 15 and 16's. So my car is going back in the end of the month and the entire drive line has to come out to replace the prop shaft which will take three days. So the problem is that GM knows that there is an issue and have no fix for the play in the prop shaft and in 4000 Km it will start again. There is a service bulletin out but they are tight lipped and are not saying much. Anyone else having this issue?