1st,,,use a Mitsu brand seal,,,,check the special parts repos on this site.
OEM seal has more sealing surfaces than an aftermaket.
It's not a very hard to do repair.
The transfer case Slip yoke seals tend to leak a bit, esp. from vibrations in driveshaft and possible slop from wear in output cover bushing and slop on output splines.

dave h.
'89 Raider V6 5spd;Aisin Hubs;; Gen2 LS: frt. brakes, rear coils;U.C.arms;R.trailing arms;idler arm; rear LSD axle w.disc brakes ;2 battery system for Dog's fan; relocated ECU; custom bumpers;J.Baker receiver;Conferr roofrack; t-bar crank.