Mystery plug above front diff
 

Hey all-

Just a 6.5 newb question- I pulled the 4L80E out of my 1500 to have it rebuilt (and give it a good bath) and while I'm pondering how I'll deal with the bolt that sheared off in the manifold, I was wondering what this lonely red plug does? It was just dangling above the front diff.

This truck is new to me and came as a sort of mystery case- previous owner didn't know too much about it either, or didn't want to say :argh:
At least there's a PMD cooler and things around the engine look halfway shipshape...

While the tranny is out I'm gonna poke around and see what else I can make useful.

Block heater plug at the block heater end.

Right on. Gonna need that! Thanks.