I have checked a lot of things out and so far no luck. It sounds like it is in the brakes. A dragging,rubbing sound. I can really hear it when I drive between parked cars or when I'm up against a barrier wall driving slow. I just installed new pads on the front and the rear are not even half worn down. I had it up in the air and tried to make the noise by turning each wheel individually and could not make it happen. The u joints were my next check but they seem good also.
It is an 02 2500HD crew cab,4x4 with the 8.1 and 130,000 miles runs great. It is just bugging me that I can figure it out. I changed the front diff fluid and it came out grey,not dirty black like I thought it would. The rear diff fluid looked normal when draining. 4x4 works fine.