Just bought truck and it vibrates at 70 mph

[ForrestGMC]

First off I'm new here so waazzzzup. Do people still say that? 

 

Just picked up a 2015 GMC Sierra SLT Z71 6.2 with only 50k miles. Has a 2 inch Rancho level and bigger tires. KO2s A/Ts During the test drive I noticed a little tire whine but didnt think much about it. The truck rode smooth with minor vibrations at high speed but again thought this was somewhat normal with the level. Still the case, but it's gotten annoying. 

 

The dealer is looking at it tomorrow and hoping to fix it. I dont think it's the "chevy shake". My suspicion is the struts, or the tires which are about 30% worn. A guy at my work said he thinks the inside of the tires are cupping. Also my Toyos 33" I ran on my tacoma made no noise. The current tires sound like M/Ts

 

Anyway happy to join.

 

Any thoughts, input would be appreciated.

 

Thanks

[Colossus]

Welcome.  And welcome to the popular shaking issue on these trucks.  Lifts tend to magnify the noise in my experience.   But some good beefy tires might do the trick I've had good luck with Cooper so far.  You'll want to have the drive shaft looked at as well.