My 2012 GMC Sierra 1500 SLT Z60 Pickup has developed the "Chevy Shake". If you don't know what that is google "Chevy shake". The information I found indicates that there current is no fix and GMC does not know why. Speeds greater than 65 MPH results in a vibration which feels like a tire out of balance, felt in the seat. Some people have gone to great length to resolve this issue, with no luck. GMC does not feel this is a safety issue so they are not compelled to issuing a recall. Just wondering if others have encountered this problem and was able to resolve it Thanks for all replies