2003 4WD Mystery
 

2003 Blazer. Four wheel drive is not working. I've checked the vacuum actuator under the battery, it's working properly. The cable appears to be moving correctly. Both 4 Hi and 4 Lo lights come on and stay on, but the front wheels do not engage. The transfer case engages into Lo range, and fuse is good.

My only other thought is to check the cable connection on the front differential.

Any other suggestions?

Thanks

Ya grab it up top by the actuator with a small pair of vice grips. If it moves more then like 1/4 to 1/2 before you feel it click it's most likely disconnected. At the diff its only connected by a crappy little clip just like under the tray.

Sounds like your t-case is working fine but your front axle isn't engaging... check the actuator cable as stated. Passenger side axle shift fork assembly could be jammed up, or more than likely its a vacuum problem... Torn actuator, leaking line(s), bad vacuum switch on the t-case, etc.

I assume I can pull the cable housing off the differential and check the cable connection without doing anything up by the actuator(??)

I'm confident the vacuum actuator it working because I started the engine and pushed the 4WD button, and the vacuum sucked up tightly and pulled the cable as it should.

Yes, think there 15mm (?)
Bring a tray it will most likely drip some gear oil.

The 1A Auto guy on youtube has some really good repair videos. He shows how to remove the housing and cable. Makes it look easier than popping corn.

In the video he disconnects the cable with his fingertip which makes me wonder if it comes undone on its own a little too easily. You mentioned the crappy clip that holds it in place. Maybe that clip came loose. I'll report back on what I find.