I have a 97 f150 extended cab lariat with the 4.6 and it's electronic 4wd. My 4wd isn't engaging so I did Some checking. I looked under the truck and the actuator didn't move when switched from 2wd to 4wd. I can hear the click from the dash and hear the shift motor from under the truck also. I checked the vacuum lines going to the actuator and I get decent vacuum on the peach colored line but the blue is very faint. So I checked the solenoids. I am getting full voltage (13.8v) on both solenoids regardless if it's in 2wd or 4wd. From what I have read only one is supposed to have power then when you switch to 4wd the other solenoid is suppose to have power.doesn't the gem runs these? If so I must have a bad gem, does this sound right?
My second question is when is the front engaged, is it when the actuator is pushed out or sucked in? Thanks

 

Have your vacuum actuators been replaced? (they're on the firewall). You live in IL. I bet they got moisture in them, it froze and wrecked them. I had the same thing happen to my truck, the fix is a replacement mount (that comes with one of the actuators) they're under $40 for both from rock auto.
You'll notice the one that looks like it's in a box, the pic is upside down, that's the fix a little hat over the top of them.





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