Any idea what is leaking?

[11zr104cobra]

Hey guys. I recently picked up this 2006 gmc Yukon Denali from the original owners about a month ago. Loving it so far. Extremely mint always dealer maintained.
Anyways I’m wondering what is causing this leak that I circled. When I first got
It there was nothing there in that spot at all. The first picture is from tonight. The second picture is from a few days ago and the 3rd picture is from when I get out off the trailer.
I’m assuming an input shaft seal or something to the transfer case? Any ideas would be awesome. Thank you.

 

[blackelky]

Might be the boot or the front driveshaft seal

 

[blackelky]

has the transfer case fluid been changed? Maybe the fill or drain bolt needs a new washer

 

[swathdiver]

Right above, transfer case output shaft seal.

 

[rockola1971]

Tcase output seal OR Tcase pump rubbing through rear half of case. Look on passenger side at the rear extentions of the Tcase directly on that its side. Feel if it is wet there. I believe BW AWD Tcases use the same pump deisgn as the NP246/NP246E which is commonly found in 4wd GM 4x4 applications.