Diff oil out the vent, why?

Mine must be way overfull too, as she is 7* nose down at rest, and oil level with the bottom of the hole. When I gas it, the pinion rises towards zero, and now she's really overfull, lol. I just like that small front pinion bearing well-lubed.
I have 3.55s, and a hump-vent. and yes I installed a long hose on it. Been like that since year 2000 or so.
But I rarely exceed 65 mph, and so, with 27s the axle rpm is very reasonable.