if you get a replacement gem unit does it have to be programmed to the truck or it just plug and play?

 

Depends what year you get one from it might not be compatible.

And no...they are not reprogrammable.

 

This is what I am leaning towards.

 

Id try to get one that matches the year and model.

 

Do you know where i should start checking the wires to see if they are bad?

 

Id trace back starting at the vacuum solonoids.

 

There are two relays (behind center of dash) that power the transfer case shift motor. These relays are controlled by the GEM. If the t-case motor is not moving check it for voltage. If no voltage is being provided to the t-case motor check these relays.

 

Do you have a diagram on where these relays would be?

 

http://www.justanswer.com/ford/3as5x...lectrical.html

 

Whoops wrong thread