More then likely the gear box needs to be vented. As the oil heats up it expands and will blow out at the weakest point, the seal.
SEW & Falk make nice motor gear box combos.
Excellent info, thank you. I had wondered about the venting, but as far as I can tell, the gearbox has one fill/level/drain hole and that's
it. As in to even change the oil you have to remove the whole unit. I just loosened the allen plug but that seems like opening
a whole new can of worms what with the air quality in the immediate vicinity.
Ours lasted 8 years. Just replaced ours 2 months ago.
Not too hard to do but that's not something you keep a spare of...$500 motor. I bet if it even had cooling around the outside of the gear box (heat sink fins / small fan) that would be sufficient enough to last 3-4x longer.
Re-sealed the one I replaced so we have that to pop in if need be, the motor was toast but the gearbox is re-usable.
I don't think cooling is an issue, the oil seals will wear out long before anything else. The problem is that when they do,
they leak into the motor, giving no indication unless you are looking for it.
The Boston Gear box on our old American has a fill and drain hole and a sight gauge and while it's never leaked if it did it would
end up on the floor, not in the motor.
