Its like a constant noise that goes on after about 30-40 MPH. It was starting to make noise at 25MPH but that went away. Then it came back after maybe 300 or so miles. The differential has plenty of fluid in it. Its not the brakes so I think its the rear axel. Its a 97 K2500 long bed extended cab 6.5TD F engine. I have no Idea what gears I have, All I know is that I think it is a Z71 because it's got a lift to it and it has the black fender flares. I have 32 inch goodyear wrangler silent armor with 17 inch rims on it. I dont know what else to say but if you need anymore info to help me diagnose my problem just ask.