I have a 2014 silverado Z71 crew cab, I have a shake from the rear end. Everything in the cab shakes between 35 to 45 and then again around 70. Feels like the seat is a massaging seat. I bought a new set of rims and used the stock tires, 17 inch. Still had shake even after 2 rebalancing. I then bought new 22's and have same shake but worse. Took to dealership, advised had three seperate set of rims and two different set of tires, two different shop balancing machines, same shake. Dealer technician noticed the shake also. Dealer had my truck from Thursday thru Monday and gave me another 2014 Silverado 4x4 to drive, same shake. When i picked mine back up they told me is was the aftermarket rims and tires, nothing they could do for me. I seen other blogs where they said GM knows about the problem, has anyone else heard if GM is working on a fix?