ImpalaGuy

I'm a auto tech for a G.M. dealership in P.A. I'm currently experiencing this same problem with a 2014 Silverado,four wheel drive,automatic, with the crew cab if that's what you want to call it. It currently has approximately 20,000 miles on it. This vehicle also has Goodyear Wrangler tires on it,20 inch and going down the road frfom 68 m.p.h and up I can feel this shake in the vehicle. I have road force balanced the tires,switched the driveshaft with another stock unit and then i tried another set of tires that were Goodyear Eagle tires. I have replaced the left side axle,measured axle runout at all four hubs,i have removed all rotors and cleaned them with a rollock wheel. This truck is driving me insane,I currently have over 20 hours trying to figure this out, I seriously don't know what to do next the customer is being very patient whichis nice of them they have been in a loner this hole time. We have had this truck for about a week and a half. Help me G.M help.