I'm just now discovering this thread. My previous gripes have been posted in the "2014 Owners with Issues" thread. This topic is my biggest issue with my 2014 Sierra All Terrain, but still one of many. It's a $50K truck that rides like a 1950's truck. The steering wheel and seat vibration from about 40-65 mph is utterly frustrating and absolutely not acceptable by anyone's standards. Mine is currently at the dealership for this and multiple other recall or warranty related issues. However, based on reading many pages of this thread I have no confidence there will be a fix for my (our) problem. To validate it further; the dealer gave me a loaner truck with 161 miles on the odometer. It has the exact same vibration and unsteady feel. I'm thinking this is a problem that runs throughout the new GM truck platform and they clearly know about it, but have no idea how to fix it, nor are they really concerned about doing so. It's easy for them to use the standard response of; "vehicle rides and performs as designed", therefore claiming the trucks are working fine by their standards in an attempt to avoid any liability. They know it's not something that'll cause physical harm to the drivers/passengers, therefore they have no worries about fatality lawsuits on this issue, unlike the other mess they're in right now.
The sad thing is that if 90% of us would've known about this issue before buying our trucks, then Ford/Ram/Toyota sales would've shown major growth because there would be about 500,000 less new GM trucks on the road right now. I'll post my results upon getting mine back from the dealer, but my expectations of a resolution are virtually none. Mine is a 4wd CC, and the loaner is a 2wd CC, both with identical ride issues. That alone shows this problem is rampant across the new platform.