Leaking around differential "cover"?

[Garbus]

Hello,

I was underneath the rear of my brother's Genesis early today to look at a issue with the braking system (which I'm going to make a post about as well) and I noticed around the bottom of the differential where the cover(I dont know if thats the proper term) meets with the main body of the diff is damp with some oily fluid. Is it possible/likely the diff has a small leak? I've tried finding a replacement gasket online but I can't seem to find one, is there even a gasket between those surfaces or is it just sealed with some kind of RTV?

 

[Gunkk]

There does not appear to be a gasket shown on the BH diff's EPD:

 

[Ozy44]

Also check the front side of the differential where the drive shaft attaches and see if you have fluid leaking down from the pinion seal. #4 in the above diagram.