Hmmmm.... Really? I didnt know that. I filled my front diff up till it ran out the hole, just like the rear. I dont get any overflow... Looks like I may though, if this is true! That is how I changed all 3 (front, rear and transfer) filled them up till the new oil spilled out the overflow-fill hole.Then I looked around some more and realized that the last time I had filled my front differential, I had put in too much as unlike the rear diff where one fills it until it runs out the hole, we can't do the same to the front diff or it will blow out the breather/vent-hose, that is what the oil that I had seen on everything was.