Four wheel drive noise

I have an 03 sierra 4x4. When I engage the auto four switch I notice a slight drag and a little worse when locked in four wheel drive. During a recent snow I put it into four and when approaching a stop without applying the brakes it made a growling/ginding noise at about 5mph. You could somewhat feel it in the steering wheel as well. This only happens in four wheel drive. Any ideas as to what it could be or what to check. I only have 35000 miles on it but during the summer I do have wider tires than factory so maybe that is causing some extra wear on things.