Outer Limits 4x4 Board

Hi everyone, I cannot get the search function to work so I hope someone will be able to point me in the right direction. I have a 12/1988 BJ73 That after my last trip out started to leak oil from the front output seal on the transfer, no biggie just replace the seal. But when i jumped under to have a look and spun the shaft over by hand the is a clicking type noise coming from inside the transfer. This case is the vacuum shift type and there is no noise audible when driving in in 4wd or 2wd. Any suggestions, has anyone else had this problem?

have you checked the back of the transfer for oil. For some wonderful reason the oil moves upwards to the front of the transfer. what i have done is boared out the 2x filler bolts and got a tube running between them. so the oil moves up into the front of the transfer then will run back down due to overflow in the front.

My transfer leaked because of overflowing and my back 1/2 of the transfer made noise because it was empty.