No. When the water, mixes with the oil, it takes days, to seperate. And even if it did completely seperate, you would still have moisture in the case, and the damage will continue, until you drain and clean/refill with new oil. If the oil looks "milky", it is time to service the trans. I change mine twice a year. Winter change, and summer change. Plus, if I see milky oil when checking the level, I change it. Remember, Oil, 4.00, Transmission rebuild, 400. So just move the decimal point, and you are there. I have the aftermarket hose style fitting in mine, so it never gets water in it, but I see them in my shop, all the time, full of water.If the vent was working properly, wouldn't any moisture boil off after the trans fluid reached anything more than 212 deg F?