gem- generic electronic module

the way i figured it was the gem was to eliminate all other possibilities, checking the fuses and switch, shift motor. you can remove the gem and open the casing to see if there is water damage. heres a pic of mine. you can clearly see the water damage on the upper part of the circuit board.

 

since there are a few people with this problem...


HOW TO REPLACE THE GEM

heres a writeup i did on another forum with pics

i didnt mention in the writeup that you need to remove the screws that hold in the fuse panel but i figured thats a given.

 

Well, I got tired of not being able to even move the truck up the driveway to the garage so I "modified" the keyed connectors going the the 2wd and 4wd vacuum solenoids, swapped the 2wd and the 4wd connectors, and the hubs locked in. Yay! Now I can at least move it to get the windshield resealed and look into the GEM module.
Just in time too, snowstorm just arrived.

 

I just bought a 1998 F150 4.6 long box, and she is a great truck, I bought it from a dealer I trusted, over the years, I asked my salesperson and manager the condition and they told me honestly, then I had a problem come up and the very next day they let go my sales manager and later the salesman. Now I have been dealing with upper management and they are not nice...
Well when I bought the truck it was promised to me the 4x4 was good, of course like a dummy I never even turned it on. But now that it snowed I tried it, with my older turns you put it in 4H and you can tell, this one is weird though, it will spin the wheels with no grab on the front, but going down the highway I can feel it kick in or I think I can when I lick into 4H, now when I put it in 4L from a standstill I can here the clunking and it seems to be ok.
How come 4H does not seem to be on when you put it in and try to make the tires spin, is it because it just grabs when it gets going or what??