Noises problem
2002 Chevy Suburban V8 Four Wheel Drive Automatic 109000 miles

When I engage the four wheel drive, I'm getting a loud growling noise when I turn. Doesn't matter if it's right or left...it's really loud. This began suddenly; I had not heard the noise at all last winter. I have not used the four wheel drive since last winter. I was trying to sell the truck and a potential buyer who engaged it found the problem.

Thanks