A Question

I have a question that is driving me a bit buggy.  There seems to be an intermittent oil leak from my tranny.  As near as I can tell, it is from the vent tube.  But here is the thing; I can ride the hell out of her, and stop for an hour or so, and just have a small quarter sized spot (if any) on the ground, if I leave it for a day or two ( or if the weather has a sudden change)  I can go out and overnight there is about 4 to 6 ounces of 90wt on the ground.
About the only thing that I can figure is there is a pressure change, or build up over time as the outside temps rise and fall and the clouds roll in or out.  So when the pressure gets too great it forces a bunch of oil out of the tranny. 

So here is my question, does that make any sense?????????????

I cant think of any other reason why it would puke out 90 wt gear oil after NOT being ridden for a couple days.  I dont have that much hair left to pull it out over this.  So any ideas, I would greatly appreciate...cause I'm not coming up with anything else that makes sense.


See ya on the road...