2015 GMC Sierra 1500 drivetrain & axles problems

I had made a complaint to chapdelaine buick- GMC that my brand new truck did not seem to go into four wheel drive. I was told to bring the truck to the dealership and they would check it for me. I was told by the service department that the truck worked just fine in four wheel drive. I then noticed that the truck seem to shift very rough and I called the service department and told them that something had to be wrong.

Brought in my 2015 GMC 1500 sierra truck in for vibrations issues at high speed of 70-75 MPH. After 4 attempts GMC corp refuses to admit that there is a safety issues in driving this vehicle at a normal rate. They continue to remove and replace the tires. I have never owned a vehicle before that such vibration is felt in the cabin of the truck, passenger seat, foot petal, etc.that is so uncomfortable, that my wife refuse to drive in the truck due to its safety.