So I've owned my Jeep since 2006 new off the lot and I've never had any issues, and have always done all the regular maintenance. About a week ago I started to hear a whirring noise coming from the rear end starting about 10mph and continues at any speed (regardless of acceleration, braking, turning, etc.). As the week went by it has gotten louder that now I have to talk over it. I changed my rear diff fluid as it was time to do that anyway but it did not get rid of the noise, but it did change the sound from being deeper sounding to a little bit higher pitch. I've checked the rear wheel bearings, and driveshaft for any play, but there isn't any. Anyone have any ideas what it can be?