I have a 2008 'burban with the 5.3 motor and it is making a whining noise when going down the road. I have tried driving it different to see if I cna narrow down when it makes the noise, and it seems to be the loudest when accelerating or keeping speed up a hill. When coasting there is very little noise. Which makes me think its when I'm putting power through the transfer case/rear end. Any thoughts?