Well well, how to put a little excitement into my day
@Karearea.
New pic - that look better?
It's a lubricant that has thrown off the coupling. Feels like a nickel anti-sieze compound. It had some road gravel mixed in to make it look very much like a cracked casting. It's also visible on the transfer case oil cooler pipes if you squint a bit.
That shaft was removed and installed when the transfer case was swapped out in my first week of ownership. I pointed this out to my agent at the first service recently and they think it's just excess coupling lube.
But it's a good reminder, thank you. I did ask the agent to clean up this area so I can monitor it. From Logsplitter's guts-and-all pics it look like the coupling contains a silver lubricant so I'm happy with the agent's assessment but I need to know that it's stopped bleeding given the 2+ cases of coupling separations.
Cheers!