Chevrolet Repair: 94 Full Size 4WD will not engage, differential output, blown fuse

Question
I recently purchased a full size 94 Chevy 4WD pickup which needed some work. I have had the truck on the road now for about 3 months with no problems. This weekend I had the oppertunity to try out the 4WD in a muddy field unsticking a new HEMI Dodge but when I pulled the lever nothing was there. I tried rocking and reverse and could only get 2WD. I have had a 76 truck since it was new and can fix it in my sleep but I know nothing about the newer systems. Can you tell me where to start looking?  Thanks

Answer
Hi Chuck,
Quite often, the front axle actuator is the problem, and although I don't endorse the product, I will send a link for an aftermarket control device. I send it because there is a troubleshooting proceedure that might help you.

http://www.4x4posi-lok.com/PDFs/troubleshootguide.pdf

I have never tried one. My trucks are all stock, and I have replaced some actuators, but the stock ones do all I need them to do.

You could have a blown fuse, a wire pulled loose, (Check right behind the right front axle tube for the wires hanging there), or the transfer case not shifting into 4X4.
When it shifts, it closes a switch on top of the transfer case, right under the passengers seat area, and sends battery voltage to the front axle actuator, sometimes called a solenoid. It is a thermal actuator, and expands, engaging a sliding collar in the front axle, locking the right axle to the front differential output.

There is an upgraded actuator that might be more dependable, but first check for voltage getting to it.

You can actually remove it from the housing, and test it with battery voltage and ground. It should extend about an inch when connected.

Van