What's this?

Bought an '88 MJ 2WD awhile back and haven't done anything to it yet and really haven't given it a good look. Was looking at the rear diff and found this. What is this piece that I have circled? It's an 2WD where as my '89 XJ is a 4WD and it doesn't have it. Also my MJ is a 4 banger and my XJ is a 4 liter. Any suggestions or is it the most obvious thing in the world?

looks like the e-brake mechanism that the toyotas use, i dunno though, just a thought

looks like the e-brake mechanism that the toyotas use, i dunno though, just a thought maybe some MJs used the same type thing

sorry for the double post

load sensing valve for the rear brakes.

weight in the bed feeds more fluid to the rear brakes.

rare to find one that actually works. Since it's hanging I'm gonna guess it's been bypassd already.