Yes - there is an oil seal in there, but to get at it can be difficult without the right tools.
1. Remove the front propshaft from the transfer box.
2. Remove the companion flange . . . The 30mm 'stake nut' in the centre can be very tight. I have made a 'stonking great' locking bar that bolts onto the flange. Using a small cold chisel and a hammer - knock the 'stake' out of its slot and then use a 30mm 3/4" drive socket with a power bar and a scaffold pole to undo the nut:
3. In this example I have removed the Transfer Box and started stripping it - this allows me to remove the Hi-Vo chain and then remove the front output shaft with sprocket & bearings. You shouldn't have to do this. The oil seal can be seen here:
4. It should be possible to remove the oil seal with the Companion Flange removed and the output shaft still in place - in which case it will look like this:
5. Hook-out the old seal and clean-up the case around the hole. I press (knock) the new seal into place with a suitable socket - and a smear of Blue Hylomar jointing compound.
6. The companion flange sleeve can become scored if you have been off-roading and got mud/grit into the oil seal. If this is bad the new oil seal won't solve the leak. I have had success with "SpeediSleeves" - very thin tubes that are pressed onto the companion flange sleeve to provide a fresh surface for the oil seal. It helps if you have a press and a lathe when doing this but that is possibly not essential. Whatever you find/do make sure the sleeve that the seal runs on is clean and without any burrs.
The oil seal is Part Number:
90311-41008 .
You should also use a new Stake Nut - Part Number:
90179-22016 .
The Stake Nut should be torqued to
87 Ft/Lbs before being 'staked' with a small cold chisel and hammer.
And there you go; I hope I haven't put you off but its as well to know what to expect - these things require some serious tools !
Bob.