Ok after doing a little research I think it is for the vacuum disconnect. Which means we have a little problem as I was told the axle was from a 99 and that only came on 91-
confirmed. that is a disconnect vacuum actuator. definately not a 99. i had a disco housing that i was going to put a later one piece pass. side shaft in. the problem i had was getting a new seal. couldn't make anything match up and work. i ended up buying a later hp housing and having it set up. good luck.
Yah I wasn't even looking for it got the axle installed luckily didn't touch the steering then I saw it sticking out like a sore thumb and figured thats what it was but didn't want to believe it haha.
Ok, he said he pulled it from a 99 so maybe someone already did the delete on it, but we are going to figure out either a replacement or refund. Said he hasn't had any older than 96 at his shop in over a year so I think this was just an honest mix up somehow.