Can anyone help.....

My 4x4 does not engage, the dash lights come on the floor shifter goes in to gear. What can it be? Checked fuse #23 it ok, blue vacume line behind batery has suction when she's run'n and i hear a click inside the cab when i put it from
2w hi to 4w hi......Any ideas any one......Or does anyone know where i can get the vacum diagram. as far as i can tell i have 1 acturator on the right side of the transfercase.

 

Place the front of the truck on jackstands, engage 4wd, once engaged climb under and check if you can spin the front driveshaft. If it spins freely the problem would be transfer case related, if it does not spin the case is locked in; your problem could be the actuator that's on the front axle. It is a vacuum operated fork that slides a collar on the axle shaft to connect or disconnect.

 

Do you hear the encoder motor on the transfer case moving?