My rubber boot on the front diff actuator is riped. does this need to be sealed to keep vaccume, cause my 4x4 does not work?

 

Push in on the actuator, then put your finger over the nipple on the side (where the vacuum line connects) and let go of the cable. If you do not feel a suction of air when you pull your finger away, the actuator is faulty.

 

I have 5 Jimmy's/ Blazers, each of them have 4 wheel drive, and if the boot is torn, cracked, or rotted away, there is not vacuum, which prevents the actuator from engaging.
But I have found a liquid (oily like) in the vacuum line going to the actuator, and this liquid breaks down the rubber, does anyone have an idea what this liquid could be I have replaced the actuator 2 times and not again till I find out where this is coming from

 

that fluid is most likely transmissions fluid search the fourm and you will find others with the same problem.