Ok .. I have pulled the battery / tray and the actuator is pulling all the way in and the cable moves freely with it. I hear the transfer case shifting and can feel it in the rear wheels in what is supposed to be 4 lo . So the transfer case is working the lights flash for a couple seconds and go solid in whichever mode I push so the switch is working .. I hear the TCCM clicking and have already checked for corrosion its working.. So why wouldn't I have 4 wheel drive? Now if I push any 4 wheel button after about 200 feet the service 4 wheel drive light comes on and then I cannot switch to anything until the truck has been turned off. Is this because the front wheels are not engaging ? I have jacked the front end up and can spin the wheels freely in every mode with the actuator pulled in .. Help !! I do get a code of C0300 rear prop shaft speed sensor and C0374 which i believe is speed senor related as well .. I have switched the sensors around replaced the rear prop one..same code.. checked wiring , cleaned connections ... I am stumped ! It worked less than a month ago with no problems or sounds.

 

Ok .. I now have pulled the actuator cable at the differential and manually pulled the "fork" . It slides out easy but with the front wheels off of the ground and I spin the driveshaft or tires it does not engage.. Guess it's time to pull the passenger side apart.

 

What year is your truck ?

 

2000 Blazer , 4 button. I replaced the transfer case( the old one the chain came apart ) and encoder recently and it worked great .