A little update on my story..
Heres my original post: http://www.gm-trucks.com/forums/topic/153186-shake-or-vibration-issues/page-91
But if you want the jist of it now, Vibration at highway speeds, dealership in my home city said no vibrations at all, planned on taking it to another dealership 45 minutes away that said thats not right.
So monday came and went by and I took my truck to the dealership. When I got there I explained to him that I am absolutely positive that there is a vibration in my vehicle because I've had a rattle "fixed" multiple times and it is fixed until I hit the highway for about 20 minutes. So I took the service manager and a service rep for a test drive, had them both sit in the backseat for a little bit just to hear this rattle in my passenger seat. Once it was established that my truck indeed did have a rattle I brought the manager up in the front seat.
We hit the highway and thankfully the passing lane of the highway has been just redone, so it was completely smooth. Once we got on there the manager noticed that the vibration was clear and so did the rep in the back seat.
So they decided to look at it, they took it for their own test drive afterwards ruling out the engine and drive shaft. Leading really only the tires left. So today they took of the tires, and tested other ones of different sizes and different makes. The vibraton was still there.
They proceeded to take out other trucks straight from the lot and test drive those, which they say the vibration is still there even in those trucks and its just the "characteristics" of these type of trucks. Even though when I test drove these when I bought one (tested about 5), there was no vibration. So I am headed to the dealership to test drive 3 from the lot and if there is even one without a vibration, they are keeping it until its either fixed or decide to give me my money back.
I will keep you all updated on it!
P.S I am really starting to get pissed of at this and I have a feeling if I take out a truck without vibration I am going to get a response something like this "I guess it's only a few trucks that have this type of characteristic"