E154F Transmission Dumb Question

Ok this is probably a dumb question but I cannot figure out what this piece is.. It is off the passenger side by the mount. It looks like there was a nipple or valve of some kind that broke off. Any idea what this piece is? And if I need to replace it?

It's a breather/vent. You probably should, that hole is letting [small] amounts of dirt in.

alltracman78":3c00rcjv said:

It's a breather/vent. You probably should, that hole is letting [small] amounts of dirt in.

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It is currently out and not running so that isn't an issue. Thank you very much!

Ok one more dumb question. Is the housing made of cast aluminium? Or what?