Leak or blow by?

I noticed some grime on my 04 manual transmission case and oil pan. It doesn’t look like a leak, I can’t see any dripping and all my fluids are full, but I can get a finger full of wet grime if I wipe with my finger. I doesn’t smell like transmission or differential fluid, and seems to be from underneath the engine not coming down from the top. Any clues as to what it could be ?

 

When was the last time the bottom of the Truck was washed clean ?

A drip here and there over a year can look like quarts of oil . Add in assorted road dirt things add up.

 

Hey thanks Bivouac, I think I’ll degrease it and then monitor it for a while.