What part of a 3 speed overdrive trans is this?

[LowGT]

Recently bought a 3spd OD trans with all the wiring and levers that came out of an original truck. Things got a little hairy during removal but i didn't see any damage. Now I notice something was broken on the top side of the tail housing, I'm hoping it was just a vent but I'm not sure. I can see the output shaft through the whole. Think I could just weld this hole closed and forget about it? I attached an image of another OD trans with the "thing" there. Anyone know what it is/ if it's important?

[old Chevy guy]

Not positive would say its a vent.I wouldn't plug it up,if it is a vent your tranny will build up preasure and leak from every seal there is.

[LowGT]

I guess I could tap the hole and put a hose barb in it, then run a vent tube off of that.

Anyone else care to take a guess what that is? I didn't find it in any of the parts diagrams for the OD trans.

[LowGT]

Here's whats left of mine.

[old Chevy guy]

Still not positive its a vent but your idea sounds like a good one.Where did that unit come from origanily? I dont think Ive ever seen such a thing.

[LowGT]

This particular unit was an option on a 69 Custom, but the borg-Warner OD units were on lots of different cars and trucks in the 50s and 60s. You don't see the OD units very frequently.