Unfortunately not. The input shaft and both output shafts have seals. There's no way to tell which one is leaking. The only way that you'll be able to find out where the leak is coming from is to really clean the entire transfer case with Simple Green or some other grease cutter, fill it with fluid, and see where it leaks out.
When my Tacoma developed a leak there were drops of fluid on the garage floor and it was really easy to tell that they were coming from the rear output shaft seal.
It could also be coming from where the actuator (black box) mates with the transfer case. If that's where it's coming from, I have no advice for you. I've never done any work on that piece.