what model trans ?
and where is it leaking ?
If it's leaking near the tail shaft where the transfer case bolts up,
the adapter bolts may be loose or the case may be cracked.
If it's near the front,,could be a front seal or the pump bolts or pump gasket is leaking..
On the sides,,could be a dipstick o-ring or a governor cover or servo cover o-ring leaking,,,,or a trans line or fitting loose.
Or the shaft where the gear selector shaft goes into the case,,,small seal there too...