If my car were turned and held upside down or any radical angle (downward, sideways) for any time, would transmission fluid leak out somewhere? If so, where would it be likely to leak? Say that the seals are good. I have the factory 5speed manual transmission,

In other words, does the outside air ever enter the gearbox while driving or seep in over time? If car was submerged in water, would water enter the gearbox? I'm trying to figure out how tightly sealed the inside of the gearbox is from the outside.

98 Civic, D16Y7

 

There is a rubber vent on top of the casings. They have to be vented otherwise pressure will build up inside and cause seal leakage. Honda made them pretty well and they do a good job of keeping water and dirt from entering.