just a quick question, on my 97 s10 blazer 4.3, there are three lines that plug into the transfer case, does anyone know what they do or what purpose they serve, because mine aren't hooked up right now

http://www.automotiveforums.com/vbulletin/showthread.php?t=343043
This looks pretty related.

they engage the front axle.
Without them you won't have 4wd

1 is vent, 1 goes to the vac actuator under the battery, 1 goes to the main vac system between the intake and the vac resivoir (sic?)