I'm trying to get an idea of what is going on with my truck before I take it down to the shop and start taking things apart.

Basically when I drive for long distances on the highway, when I turn the wheel sharply, like to turn into a parking spot, and start to drive, it vibrates bad like I have a flat tire or something and makes some noise. When i first get in the truck i can turn the wheel as far as it will go and turn with no noise or vibration. But if I drive on the highway for 20 minutes or longer it starts acting up when I make sharp turns(sharper than a 45 degree angle), and it gets worse the longer I drive.

I'm going to take it to my dad's shop and get it on the lift and try to check it out, but I figured I would see if anyone could give me some ideas on what to check. Maybe it is a common problem or something for awd. Thanks

 

I believe you are going to find out that your viscous coupling in your transfer-case is going bad. It is not allowing slip, in turn locking the front and rear axles together, making the truck act as if it were a true 4WD causing the typical crow hop feeling you are getting.

The viscous coupling is/was available for replacement, but your transfer-case will need to be torn down for replacement. Another option would to be find a suitable replacement, they do come up for sale from time to time. Lastly, there may be re-builders that handle NVG-149’s that you could get a fresh unit from.

The list of vehicles that the NVG-149 came in is reasonably extensive, so you have a decent shot at finding a replacement.
’01 GMC C3
‘01/’02 Yukon Denali
‘01/’02 Cadillac Escalade
’03 thru ’05-1/2 Silverado SS
’02 thru ’07-Classic Sierra Denali

 

+1, I'll bet that's exactly what's happening, it's like driving in 4wd on dry pavement