I am guessing there is still no fix for this issue? I have had the same issue with my 2014 Chevy Silverado Crew Cab LT ever since I hit around 8k miles. I am now at 12k miles and have had my truck in the shop 5 times, at two different dealerships, still not fixed. At the first dealership, my tires were replaced because they were "out of round", my drive-shaft was replaced, checked my alignment and road force balanced my tires. After none of this worked, the dealership concluded that the vibration was within GM's "quality standards" and there was nothing else they could do for me. The second dealership said they had a new "vibration sensing device" that was sent to them by GM to detect issues such as this. After running their tests, they road force balanced my tires and called it a day. This is my 7th GM truck and I have never experienced such a rough and annoying ride quality, this truck drove like a Cadillac when it was first purchased.
Has anyone tried filing Lemon Law for this problem? This will be my next step and if that doesn't work, I will be selling my truck and switching loyalties.