I have a 95 blazer and I found out today that the 4 wheel drive is not locking in. There are no blinking lights on the switch and no codes detected on my GM tech 1. When I activated the 4x4 high and low, the front drive shaft will not spin by hand like its engaged. When in 2 wheel drive, the drive shaft will spin freely by hand. When I am stuck in the snow, the front wheels appear not to be locked in, or grabbing traction. Just the back wheel are spinning. Any suggestions? The vacuum hoses look ok, and the transfer case seems to be making that clicking engaging noise when I push the 4x4 buttons.

Thanks
bizzs

 

Your transfer case is engaging. Under the battery tray is a vacuum actuator that engages the right front axle with the differential. When vacuum is applied to the actuator, the front differential is powered for 4WD. There is one vacuum line attached to the actuator. Engine at idle, trans in park, 4WD selected: The vacuum line must have manifold vacuum. Post your results.