Transfer case fill plug

[Marshal]

Hello, I have to replace the transfer case seal on my 1993 L300. I am having trouble finding the seal in Calgary so I may have to order one from out west. In the meantime, I need to top of the fluids and on the top of my transfer case there is a rubber plug that is easily pulled out. Can the fluids be filled from this point? I couldn't find anything in the search regarding this plug but I have taken a couple pics and posted below. If not for filling the transfer case, what is this plug for?

Any help would be appreciated,

Thanks,

Ryan

[Growlerbearnz]

I think that's the breather.

The fill plug is on the side of the transfer case, it's like a differential in that you fill it until the oil level is just below the fill plug. If you fill it from the top how would you know when the oil was at the correct level?

[Marshal]

Good point, thanks.

[sealica]

Just wondering about my transfer case breather. Mine seems to be plugged because there was some suction when replacing u-joints ... should popping it out and cleaning it suffice, or has anyone replaced this with a better one? figure it's a fairly common size (metric vehicles) or likely to be a mitsubishi specific OEM thingy.

[Growlerbearnz]

It's not your traditional free-flowing breather, it's more of a pressure relief valve. It's a rubber mushroom which is always lightly closed to prevent water getting into the transfer case, but will vent slightly once the pressure overcomes the rubber seal. It relieves pressure more readily than it relieves suction (presumably to stop water getting in). There's always a feeling of suction when removing the driveshafts.

It's supposed to be glued/silicone sealed into the transfer case's top cover, so be gentle if you're trying to remove it. On mine it just pulled out easily, but the identical one on the manual gearbox split, leaving a chunk inside the gearbox. Which wasn't an issue for me as I had the gearbox in pieces and a spare breather on hand.