First just make sure your diff oil is a normal colour. Take the diff and try to move it around and make sure it does not move any way. Just finished rebuilding my front diff. The carrier bearings went in it. Noticed this when i changed my oil, the diff had excessive side to side movement. If you really wanted to you could measure backlash and check you gear pattern. If its a whining noise i would check your gear patttern and make sure it is normal. Haven't had much to do with the rear diffbut i believe starquest is talking about the c clips holding your axles in, unless you running larger tires i don't think they will be your problem. I'd start with checking that pattern. Let us know how you make out.