Thanks to Hanr3 for the following thread: https://blazerforum.com/forum/tech-a...will-help-7180 (4x4 No Worky... Maybe this will help...)

This helped me track down a kinked/flattened vaccum hose. After installing a 2" body lift, i noticed the 4x4 wasn't working. Additionally, the HVAC controls were not working- the dash would blow but when i changed it to feet or defrost it didn't move to the area selected. After reading this thread I understood that both the 4x4 and HVAC controls work off the vaccum created by the motor. I traced the vaccum lines back to the top of the intake (drivers side just above the oil cap located on the valve cover). I found the vaccum line flat and worn. I'm guessing that as the body lift raised the body above the motor it was enough to kink or flatten the vaccum line. I placed a new piece of hose and the Blazer is back in business just in time for another 8-10" of lake effect snow expected tonight in West Michigan. This is my daughter's daily driver for school so working 4x4 is important to me. I have used this forum to trouble shoot multiple items and repair them on my own.