The front diff takes GL-5 gear oil, usually either 80W90 regular or 75W90 synthetic works. That one it is most likely the 22mm or so plug on the front diff with a copper sealing washer.

 

ATF in there won't hurt anything, but it is not best for that application, because it really needs the extreme pressure additives in the gear oil to adequately protect the gears. Otherwise they may wear prematurely.

Its either a 21mm or a Torx T70. I know this as I do fluid services on Subarus all the time.

Front diff capacity is roughly 2.5 pints.

Got the stuff for it. All except the Torx t70. Where would I find one? So far Menards, Farm & Fleet, Home Depot and Autozone have been tried. Closes I found was a T60.

I got mine from Snap-On and actually I don't really know where else to get one personally.....

Did you confirm it's torx? If so, Ace hardware, Sears or Harbor Freight come to mind

T70 probably you'll have to order, that's just a little too big for most places to carry it. Tool trucks would probably have it, given that Subaru and maybe other automakers are using them for drain plugs now.