Ill give you a bump man, someone has to know this. It would be nice to have a DIY if someone has the answer...

 

I just did this in my S4 last week. From what I could tell the Front diff and the trans share the same fluid reservoir. I drained the fluid from both of those bottom plugs that you have in the pic, and then pumped in the fluid from the filler hole on the side of the diff by the cv axle....Its been running fine.