4wd rear transmission seal r and r

[melmount]

I just noticed on my wifes truck its leaking tranny fluid. The transfer case is all wet. I filled the transfer case to its proper level 8k ago. Its still full. I believe its the rear transmission seal. Its not the pan, lines or anything else.
The back of my trans on this truck has a cast iron adapter piece approx 6 inches long. That bolts to the tranny and the transfer case bolts to it.
Where exactly does the tranny end? transfer case begin? Basically, whats the cast iron piece?
Where are the seals? The transfer case is a sealed unit? the trans is too?
YOu dont fill the cast iron part so that must get its fluid from one of the two?
which one? I am assuming there must be fluid in the cast part?
I have never looked at the back of a 4wd trans before with out a transfer case to it.(well, its been a while.
CAn someone explain? I willpull the transfer case and replace the front seal in it? I assume its like a pinion seal?Must be similar on the back of the trans?
thx

[melmount]

bump.........