What the heck is this?

Running down a pretty good leak on my 95. R150 tranny. Pic is from the passenger side. It looks like a vacuum line, but on manual? There was a cap on it, but it seems to be the culprit of the leak....

 

Welcome!
Is it actually trans fluid?

 

Definitely gear lube and it's coming from the top. Pulled the shifter off, as there was a ton of fluid around it. I can't imagine that much fluid coming from there though. You don't even need a gasket there. You can watch a pretty steady drip after she is warm and is parked.

 

Is that the transmission vent? Hard to tell from that picture.

 

I don't think so. There is 3 separate vents on the very top. This was capped with a little rubber cap, but it was very loose and somewhat dry rotted.