4wd Noise

[bwibbeler]

Here's the scoop....I noticed approximately 3 weeks ago a strange howling noise inside the cab of my truck when I engaged my 4wd high. It seemed more noticeable when reducing speed as compared to speeding up. I brought it in to my local repair shop to see if they could diagnose the problem. Upon inspection, they felt the bearings were out in my front differential. I gave them the ok to open up the diff and replace what was needed. Well, the repair was complete and guess what, that wasn't it. They took it upon themselves to open up the rear diff and replace the bearings and seals in it.....let's just say that wasn't it either. So, let's move on to the transfer case...opened that up and found nothing "wrong". The last I heard, they are in the process of trying to figure out what the problem really is $$$$$$$$. Anyone have any ideas as to what this may be? 2003 Sierra 1500HD