I have a strange noise from my 200k 07 Burb diff. No howl, locker seems to work fine. Only happens with foot on the gas and goes away when foot is off. Sounds like cats fighting in the rear diff or a rusty brake caliper inside! I listened with a stethoscope and it seems to be coming from the rear diff cover area, but hard to tell. Wheel bearings were quiet. U joints tight and quiet. The pinion is quiet and leak free. It's smooth on the road and the diff seems a little warm after a long drive. Fluid is clean and clear and there was some Very fine metallic dust covering the magnet. I have never heard anything like this. It's almost a scraping sound. Any ideas please let me know. Carrier bearings? Pinion shaft worn? Worn pinions? Locker pending implosion? It's been a highway only vehicle and serviced regularly. I have a google video of it here: https://photos.app.goo.gl/hwgbHWYSxEZCRzrj2

 

Turns out it was the pinion bearing. I rebuilt the diff last weekend replacing all bearings and seals. Everything ended up within spec and the noise is gone. Rear end is silent now!