Hey guys, recently while driving the mustang around I have notice a clicking noise coming from the rear end. Almost like a card in bike spokes. You can't hear it from inside the car unless I drive by a guard rail or something that echoes it, but outside the car its easily noticeable. I took off the brake pads, calipers, and rotors and spun the axle by hand and it sounds to me like its coming from the differential. Any ideas of what it could be, or where i should start. A couple people i asked mention the wheel bearing, but i thought they more squealed/moaned when they go out. Any input would be appreciated before i tear into my rear end. also it has 75,000 miles on it and i have never touched the differential.