Shift Shaft Seal questions

I agree 100%, there should be no added pressurization of either sump from other factors. If there is any tendency for fluids to leak in one direction or the other, it would be due to hydrostatic pressure (due to their relative heights) and viscosity (resistance to flow) of each oil . I believe the resting engine oil level is higher than the gear oil level and the engine oil is most certainly less viscous, so if the fluids wanted to swap space at rest, I'd put money on the engine oil wanting to get into the gearbox.

Somewhere I have it written down which direction the cups on the seals are supposed to face for a 308/328 but I can't find it. Pretty sure it was cups facing into the engine on both seals, which may line up with the hydrostatic pressure and viscosity theory I just pulled out of my butt (curse of being a mechanical engineer).

 

Maybe this might also help.

https://www.unobtainiumsupply.com/Downloads/Service%20Procedures/Quad%20shift%20seal%20installation%20tips.pdf

cheers, BB