I have not seen anything posted here but have not done an extensive search. I was having a problem with the by Canyon, which has 6,300 miles on it) having an a shudder that I could hear and feel while trying to maintain highway speeds. When gently accelerating to get from say 64 mph to 65 mph the shudder would occur. Talk to the salesman (used to work in service so knows the technical stuff) and he found something that described the problem perfectly. Vehicle is in the shop now. It sounds like it may be in the torque converter and GM is recommending a different type of fluid. Won't know for sure but it could also be a bad torque converter. Just wanted to share in case anyone has experienced this or in case you have it in the future. May be limited to the 2017 and 2018 with the 8 speed transmission. Hope to hear something soon.