What is this wire?

I don't remember unplugging this from anything when I dropped the tranny, can someone help me out? It looks like just a terminated spare circuit on the harness but I don't know why it would then lead into the housing. Thanks!

 

That's the breather tube. I don't have a manual so I don't know exactly where it attaches to the body. A search should tell you.

 

Transmission vent, it attaches in the engine bay on the drivers side kind of under the master cylinder. The vent for the front diff is right next to it.

 

Not a great picture but you can just see them here circled in red.

 

Amazing, thank you all so much!!! Glad I didn't break something off, and also that I asked.

 

Looks like a clogged shitty one way original transfer case breather valve going to the transfer case through a hose.

 

While you have it out it would be a good idea to check/replace the breather hose going to the Transfer Case Actuator.