Leaking 833 Vent

Do not plug the vent because in a short amout of time every seal will be leaking in your trans, meaning complete tear down.
The tranny has to vent, because the oil churning in the transmission will make bubbles, which make pressure and have to go some where.
You could possibly un-screw the vent and make a vent extension like 4x4 trucks have on their differential and run it up higher on the car.