I have a 2000 ford f150 with the 5.4 triton. About a month ago my four wheel drive stopped working I did no know at first because I would switch it to 4x4 mode the light would click a few times and then come on and stay on. I later found out it was not working when I couldnt get up a hill. Just last night I looked at fuse 23 i think which was i the four wheel drive fuse (i think) but that was fine. I then took the vacuum line off the 4x4 engaging solenoid and the bottom hose which after doing a little research i found out was the supply hose and that was sucking air like normal. So i looked at a youtube video and it said to just connect the bottom hose not the top one and start the engine and turn it into 4x4 mode then the top part on the solenoid should start sucking air but when i did it nothing happened with the top one. But i have no clue what to do know i dont have a test light or anything so i cant check if power is getting to the solenoid. I heard that the GEM modules go bad and my wiper blades will come on when i dont hit the switch periodically but work fine when i hit the switch. Any help would be awesome thank you!!

 

Well I would start by looking at all the air tubes going from the solenoids down to the actuator. I found a crack in mine under the battery tray. If those all are good I would go get a test light, they are cheap and test the power to the solenoids in 4wd and 2wd. I got my solenoids off of amazon for cheap. Took me about 30 min to replace them and fix the lines then boom! 4x4 works again. Not bad because I negotiated $500 but off the truck because it wasn't working.

I think the gem going bad is highly unlikely.

 

I have checked all the lines and bought a test light and tested the lines going to the solenoid and they are fine. What about the vacuum actuator on the front driveshaft

 

It could be that although it is more rare. Could be the forks in there as well. If there is the smallest leak in one of those hoses, it will not operate. Mine was the size of a pin hole and I only found it by having the truck running and feeling every inch of the tube. Then I found it right by the battery.


When the truck is on, only plug in the bottom hole on the solenoids. Vacuum should be present out of the top hole of the solenoid on one when in 2wd and then on the other when shifted into 4wd. If this isn't happening then they are bad.

 

I did that vacuum test and the solenoid for the four wheel drive was not working but i couldnt test the plug in because the metal part on the test light was to thick to touch the connecter

 

Neither solenoid works? Look the solenoid with pink line that is the one that keeps the front diff disengaged. When you activate 4x4 the solenoid shuts off that vacuum to the pink line, and turns on the other solenoid so vacuum is present on the blue line. You are sure neither line has vacuum whether or not you have 4x4 selected?

 

The vacuum engaging solenoid was bad I replaced it and the 4x4 works fine now

 

I have a 98 and had problems with this as well. I replaced mine with a cable operated one from Posi-Lok. Now it works no matter what and I can use 4 low in 2 wheel drive if I need to.

 

nice work mate.