So today I battled my rear diff actuator, again. Another story. But I think I need a replacement locking diff at this point. When I pulled the actuator I found lots of black sludge on the gearing. In pics from the last time, I did not see this. That was 70k miles ago and I used Castrol BOT 720 then and again today. Notes show the last time the fluid "looked good" and it was not long after purchasing at 105k, so it probably was done at least once before. This time it was really dark but still transparent. BOT 720 is pretty much clear when new. So here are some pics, what ya think? I did scope the diff itself a little, much cleaner looking than the actuator gears. I am thinking carbon clutch material and time for a rebuilt one.

edit: Just adding that the magnet was pretty minimal, no material even in the center of the magnet and no large pieces of metal.