Chevrolet Repair: 1989 s10 blazer 4wd issue, s10 blazer, coupling device

Question
My front hubs won't lock in when I engage the 4wd. When I pull the lever I hear it switching but the front wheels won't go. I know all about the vacuum and actuator but I tried to bypass it by manually depressing the actuator and placing vice grips on the cable to keep it "engaged".  This still didn't make my front hubs lock in. What could be wrong?

Answer
HI ADAM, THIS SOUNDS LIKE THE COUPLER IN THE FRONT AXLES,LOOK ON THE FRONT DIFFERENTIAL AND YOU WILL SEE A COUPLING DEVICE THAT  LOCKS THE 2 AXLES TOGETHER WHEN THE CABLE IS PULLED, WHICH SLIDES OVER THE AXLES AND LOCKS THEM IN PLACE...CK THIS AREA OUT AND GET BACK TO ME. MOST TIMES THIS COULPLER LOCKS UP AND WILL NOT MOVE TO LOCK THE AXLES TOGETHER..LET ME KNOW,,TOM..