Diff oil out the vent, why?

Demonic said
Just make sure it's clear. I had the one on my 71 Jeep and it got plugged. It was off the road for a long time before I drive it. On long trips, it would push oil past the axle seal from the extra heat of the ride as 72bluNblu mentioned.

RustyRatRod said
What method are you determining that it's not over full?

pull the fill plug out and it does not run out. The fluid is 1/4" to 1/2" below the plug. The ent is not plugged.