Not trying to call you out for giving false information, err wait, I guess I am. But have you ever opened our 4runner's service books? If you fill the front diff to the bottom of the threads of the fill hole, you have over filled it.
To the OP, a lot of people experience this after doing service. I would recommend checking your "check" valve that's on the end of the breather. A lot of time it won't let the fluid go back down the breather due to air bubbles and then it will just come out next time the front diff gets warmed up.
Well Dude, yes, I own a FSM and I use it all the time. But for this question, I didn't even need to reference it to give the OP correct information because I've filled many differentials over the years. So, sorry to disagree right back at you, but you read the FSM wrong.
It says when you check the level, if it's within 5mm of the bottom edge of the hole, you're ok. Then it says if the level is low, add oil until it begins to run out of the filler hole. Just like [MENTION=10169]TheDurk[/MENTION] already said and what I said, you fill it until oil starts running out. Do you think auto techs are going to put the fill tube into the diff filler hole, pump a little bit, stop, check to see where the level is, oh it still needs more, fill some more, stop, check to see where the level is, oh it still needs more, fill some more, stop, oh shit, it's 2 mm from the bottom instead of 5mm, better get the suction pump out. See where I'm getting at. Here, I'll say it again for your benefit and you can quote me on it,
"On level ground, you fill differentials, transfer cases, and manual transmissions until the gear oil reaches the bottom of the threads of the filler hole and oil starts pouring out."
Now, the FSM, doesn't actually say it in the Suspension and Axle pages in regards to the front differential, but I can guarantee when you fill it, it's no different than the rear differential or transfer case. What the picture is showing you is they recommend the level be within 5mm of the bottom of the fill hole. But when you fill it, you fill until oil starts running out. Any Auto Tech or DIY mechanic knows this is how you do it.
I don't mind being corrected when I'm wrong, but at least prove me wrong when you call me out because you sort of look, err wait.... Should I say it? I guess I'll be nice.
Here's a few pics that back up the information I gave the OP was absolutely correct.
FRONT DIFFERENTIAL
TRANSFER CASE and FRONT DIFFERENTIAL
REAR DIFFERENTIAL
arty: