I need some help troubleshooting my 94 blazer's 4wd. I have tested everything all the way to the differential. I have the push button and when I push 4 hi the transfer case shifts and the front drive shaft is engaged. I get vacuum through the switch on the transfer case to the actuator under the battery and the cable appears to move. I get some noise from the differential when all 4 tires are off the ground but they fronts never lock in. What is supposed to happen in that differential that is not working and what do I do next to get it working. I have tested the actuator by turning the 4 hi on and it sucks the bladder in I then pulled the vacuum line off and put my finger over it this help so the bladder has to be good. I don't know how to test if the cable is good.
any help is greatly appreciated
kevin