I have a 1998 blazer that left us stranded the other day. Front transfer case would not engage. I removed the battery and tray and noticed the cable nipple was not attached to the actuator.
I reattached and thought it was going to be an easy fix. Started the car and BEFORE selecting the car into 4H the actuator received vacuum and pulled the female portion from the male cable nipple. Were does the vacuum to the actuator come from and why does it have vacuum without the 4H button pushed. Also why did it aggressively pull the actuator from the cable. I heard mention of a switch possibly on the transfer case that 3 vacuum lines attach too. Could this be the culprit?

Any advise as to what to check next would be appreciated.

Thank you,
John