I noticed this yesterday and was wondering what it's for and if it should be plugged into. It normally hangs down near the firewall
but I propped it against the heater hose for the pic Attachment 148922
IF IM NOT WRONG THOSE GO TO YOUR 4X4 AND CARB IF YOU HAVE CARB. MINE WERE ALL REMOVED ONCE I WENT WITH THE POSI LOCK AND WEBBER CARB. I HATE THE VACCUME SYSTEM ON THE YJ'S
That is the relief tube for the vaccuum shift on the front axle CAD (Central Axle Disconnect). When the vaccuum is switched to engage, or disengage the other side needs to have a relief so it can compress. That is what provides the relief. That is all switched on the side of the transfer case. 4 vaccuum lines into the switch, 1 for vaccuum, 2 to go to the CAD (1 for each side of the diaphram) and one for relief when it switches.