[mjs2011]

I've got a QA42A snow thrower, and it has the gear box with the cast cover plate with the threaded port in it to add gear oil. However, my plate has 2 threaded ports in it, at different heights. I assume one of the ports was added by a previous owner.

So my question is, which of the two ports is the original port that I should fill the fluid level to. The lower or upper port? I'm in the process of putting a new bearing and output shaft in the gearbox, as the current shaft keyway was FUBARed pretty good. When I'm done, I plan to fill the box with 80w-90 Gear Oil. I'm just wondering which port is the correct port for the fluid depth.

Pictures attached.