I have 98 5.4 with 4x4 lever on the floor. Most of the time I can't get the dumb thing in 4x4. After much playing and experimenting/troubleshooting, I've tracked it down to something in the transfer case, whether it's the switch itself or something in the case I'm not sure. which is why I'm here now.

It seems with high probability that I can get it engaged on a cold start. If I've driven for any length of time... say 5-10 minutes. I can't get it in gear. Even when it's cold if I baby it into gear it can be slow to kick the switch on (aka the light comes on which activates the vacuum), If I show the lever who's boss it'll kick right on. If it's been driven for a while fu getta bout it. On an attempt after driving for a while...I'll here some light clicking or griding but no dash light or engagement. If I can get the light to come on.... it always engages. I'm about ready to bypass the switch and put my own dang switch inside the cab.

I'd like to pull the switch out and take a look at it...maybe test it, but how in the world do you get any tools into it? I've had the connector off and can see the wired end looks ok and dry, but can't get to the switch end. Are there any diagrams that shows what makes the switch turn on? It seems temperature related, but not sure how. Is the switch dependent on fluid level, or is it strictly mechanical?

 

Seems most people have electronic version and a simple vaccuum issue. There just seems to be no way to get at this switch to remove it. I was thinking an open end wrench with just an opening for a ratchet extension (sears version here) might do the trick, I don't have any though and hate to buy some if they're not going to let me get enough torque on it.

 

A 23mm deep socket will take the switch off. The switch grounds the GEM. When the GEM gets the ground signal from it shifting into 4Hi it energizes the electromagnetic clutch and then the front axle engage solenoid. If the switch is defective it will not signal the GEM and the front axle will not be engaged. There should be two wires to the switch one is gray. Ground it to see if the light turns on. If it does most likely the switch is defective. The second wire grounds when the t-case is shifted into low. This signals the PCM to change the automatic transmission shift strategy so you don't bounce off the rev limiter during shifts at WOT.

 

Thanks for the info and explanation of the switch. I finally got it out with some luck and various wrenches. tested the continuity on each pin. The 4x4 hi was working, but the 4x4 low was not. When pushing the ball in on the end of the switch, continuity is activated, but when releasing/depressing the ball it seems to catch about a half a millimeter from the end of the switch. If I play around with it, I can get it to snap back out the end. Continuity on 4x4 low pin is still broken no matter how far the ball is pushed into the switch but it seems like odd operation for the ball to catch on somthing like that, but then I also don't know how the switch determins which contact is grounded, so maybe it's normal operation. Seems like maybe it is grounding both pins at the same time, so the GEM might not know what to do with that situation. So it just doesn't do anything. Reason being, is I hacked the connector and cut the bad pin off and wired in temporary wire into the cab (dealer was closed). Didn't hook the wire up to anything yet, becuase it was 4x4 low line and I'm getting 4x4 high to engage everytime and even after I've driven it for a while. I drove home last night in 4x4 high in the fresh snow and I pulled in the driveway and engaged/disengaged a few times as expected. So I think I need a new switch.

Autoparts stores don't seem to have access to this part and it was too late in the day to call my local dealer. The part number on my switch is E6TZ-7E440-A (E6TZ7E440A). Some searching around online determined this part was replaced by 3L5Z7E440AB (SW6275) I found it online for as low as 21.43+s/h to 36ish+s/h, I'm going to wait till monday and call the dealer to see if I can get one a bit sooner and not pay s/h