I also have a hole in my transfer case which i just found last night. Used some JB Weld on the hole and topped off the fluid today. Will see how long it lasts.
Per mechanic friend, repair will run about $1k getting a used case to replace.
Cause based on this friends experience (as he replaced one a month ago for the exact same reason - literally same spot, same type of hole) is that there is a clip in this area that holds a pump. Clip comes loose and allows the pump to vibrate. This vibration works a hole through the case.
I contacted dealer today - waiting on thier response. I have 105.3k miles on the vehicle. Obviously this has happend before as he told me the new clip inside is a lot better.
In the first picture, you can see the hole across from the top bolt. Go left of it, down the first ridge. Second pic is close up of the hole.