Currently my 2018 Colorado has been sitting at a dealership with a vibration problem after the flush.The dealer told me they don't have a transmission tech to asses the problem, I told them i would get it towed to another dealership that has a tech.GM customer care did not like that idea because the dealer told GM customer care that it was safe to drive.I told GM customer care that the dealer had no right to tell you if it is safe to drive because they don't have a tech to asses the problem. So i gave them a couple of scenarios to think about. 1st scenario i pick up the truck drive away no problem untill i find a tech to repair the problem. 2nd scenario i drive the truck away, the problem with the vibration causes me to lose total control of the vehicle, i wind up hitting a school bus full of kids killing them all. Ya the truck is still there and it seems no one wants to to get back to me concerning this problem. My son owns the all new AT4 and guess what he has the hard shift problem in his transmission too not sure what he is going to do yet becuase he bought it at the same dealership my truck is sitting at good luck with our problems. Don't be afraid to use my scenarios with your dealership when you bring it in for your problem.