Originally Posted by a1racer

put it back on with a zip tie to hold it on if it looks cracked or broken replace it and get some tiewraps to get it secured and make sure you leave slack for the axle to move up and down

Originally Posted by 5-90

You may have grit - flush the gear surfaces and such down with brake cleaner.

I haven't figured out what size to use yet, but I'm planning on getting rid of that press-in plastic fitting and drilling/tapping for a pipe thread, then screwing in a brass pipe thread to hose nipple fitting. Probably D&T for a 1/8" NPT, then get a fitting that will take that hose (what is it - 1/4" ID hose?)

I want to do something like that for all of the breather lines, just because I don't care for plastic where it gets abused.

As far as gluing it in - it didn't need to be from the factory (it would have snapped into place,) but you'll want to use some RTV to make sure it stays put this time. Since it came out on its own once, it's likely to do so again.

A vent tube will invariably be near the top of the case, since it's not supposed to pass fluid in either direction. It is there to allow for pressure relief as the assembly gets hot (so you don't blow a gasket or a seal) and to allow air to re-enter when the assembly cools (so you don't suck a seal out...)