Hi Mark,

yup, possible to push oil out that way if the vent tube is plugged. Is it
trans oil you feel? There is a O-ring seal on the speedo shaft just at diff.
Vent tube is on top/front of diff, 1/4" diam black hard plastic, goes up
into area behind spare/rad. just pull it down and inspect, then slide back
up.  I have heard of 4x4 folks putting small fuel filter on end of vents to
avoid clogging somehow.

If you are generating a lot of pressure, enough to vent via speedo, you may
have water inside diff, whipped in a foam with oil, fills diff,  and then
able to get out of speedo, which is high up on dif. well above normal oil
level. Heat from VC will boil the water and produce the pressure!

 I hope I'm just full of sh*t about this, but if you want to check, let it
cool totally, get a small container and remove the drain plug and catch a
couple of ounces of oil. If there is water in it, it will have settled to
plug when cold. Good idea to make sure fill plug can be removed first! Just
in case you spill it all and/or the diff needs new oil.

bye, Tim