Yeah, that happened to me. What I believe typically happens is a c-clip that holds the stub shaft inside the axle housing comes loose. Since our hubs are locked 100% of the time, the diff fluid slowly leaks out as the axles spin, eventually leading to diff failure. $5 part, $2000 axle assembly, replaced under powertrain warranty. Anyone else feel free to correct me as it happened to me over a year ago and I can't quite remember if that was what my SM said.