2013 Chevy truck vibration?

Some time ago, I recall reading about an issue with some kind of frame vibration in new trucks -- can't remember if it was the 2013 GM or not.

I know a few guys on here had a problem with something - and dealer could not figure it out ... several actually. It's sticking in my brain, but I can quite grab it ...

Anyone recall it - and the fix result ... Thanks ...

Or point me to that tread - those threads?