There are two shift relays in the engine compartment, they should be near the power distribution box in a separate little box by themselves.

One relay spins the shift motor one way, from 4x2 into 4x4HI, and from 4x4HI into 4x4LOW. The other relay spins the motor the other way, from 4x4LOW into 4x4HI and from 4x4HI into 4x2.

This is the schematic for my 2001, from my 2001 service manual cd.

 

There are two shift relays in the engine compartment, they should be near the power distribution box in a separate little box by themselves.

One relay spins the shift motor one way, from 4x2 into 4x4HI, and from 4x4HI into 4x4LOW. The other relay spins the motor the other way, from 4x4LOW into 4x4HI and from 4x4HI into 4x2.

This is the schematic for my 2001, from my 2001 service manual cd.

 

NOW THAT'S WHAT I'M TALKING ABOUT!

Thank you Krewat! I'm going to spend a few minutes outside with my mulimeter. I'll report back shortly.

 

did you pull the switch out and see if it is working. that may be an easy first step.

 

Yeah. That's where I started. Works fine.

I'm thinking that the schematic you gave me, Krewat, is different than on my 02. Do you know where I can find an 02 specific schematic online?

 

No idea, they removed the on-line manuals from easy access a few months ago.

 

Schematic or not, go to the transfer case and find the solenoid/shift motor and start checking there. Do you get voltage at the plug when you should? Have a helper turn the switch while you check with a voltmeter or test light. I assume the truck needs to be running for this.

 

Oops. I already checked for voltage at the T-case. Nothing. I thought I had posted that earlier, but upon a quick review, I realize I hadn't.

Here's what I've checked so far:
Fuses. They're fine.
Switch. Voltage present.
Motor on T-case. No voltage.

I know that the problem has to be in between the switch and the motor, but I'd rather not tear my whole dash apart to simply trace a wire back. I was hoping that I could find a schematic online, but it's beginning to look like I may have to go pester the local Ford service department to see if they'll give me a copy. I've done that before for Chevy schematics, but never from a Ford dealer. Do they have a problem with letting out that kind of info?

 

Then, assuming you checked it properly, odds are on the relays or the 4WD module/GEM, but as you say you need to find them. Can't help you there as I don't know the difference in the model years. On my '05 the relays are in a box under the hood up in the corner by the windshield and drivers side fender, and the 4WD module is behind the glove box.

Fuses: In my '05 manual I am counting 6 fuses that are shown in the 4WD system schematic. You may have more fuses to check than you think?? Verify fuse continuity with ohmmeter, too.

I can send '05 manual pages to you, but I don't know if it will help or not as the whole tranny is different (Torqshift vs 4R100). PM me with an email address and I'll send PDFs, if you think it will help.

-Dave

 

Thanks for the offer. I may take you up on it later. Tomorrow I'm going to head over to the dealer to see if they'll part with the schematic.

I did check the fuses with an fancy schmancy fuse tester tool. They all showed to be good.

 

this could be a very simple problem, this past Dec I had a similar problem with my 05 F350, PS 4X4. The wife had been driving through some snow drifts and had put the truck into 4X4 low. This got her through the drifts but when she got back to the highway she could not get the transfer case out of 4X4 Low no matter where she put the selector switch. As it turn out after freezing my fingers, it was one of the relays as the previous posters mentioned. On my '05 these relays are located in a small black box between the driver side battery and the inner left fender well. The cover on the box snaps open and exposes the relays, very easy to get at. The relays simply pull out of the socket. My particular failure mode was where the relay that drives the servo motor from Low to high or 2X had failed so when you try to get the transfer case out of low the servo motor did not get voltage applied. The relays just switch the polarity on the servo motor to run the xfer case to either of the directions. Sounds like in your case the relay that drives the tranfer case from 2X to Hi to Low has failed. This is only a $15 part.

The way I isolated the problem was, I first removed the connector on the servo motor on xfer case (two wire connector on xfer case) then used a battery charger to apply 12V to the MOTOR terminals. The other multi lead connector is for the dash indicator, leave that connected. By switching polarity of the applied 12V on the MOTOR terminals I was able to confirm that the servo motor could drive the xfer case from 2X to hi to low and back again. Now I knew for sure the servo MOTOR worked because I had a helper also observe that the indicator in the truck was also indicating the changes in xfer gears. I reasoned that it now must be either a fuse or the relays. The mystery question was where were the relays and the fuse?? In desperation and with frozen fingers I paid Alldata the $25 for access to their information data base on the internet. Alldata save my fingers from frost bite. I download from their web site the schematic and component location quide. It was now easy to located the fuse, verified it was good, located the two relays and verified one was bad.

The real challenge, getting a GOOD relay. I went to the local Ford dealer, they even had several relays in stock! I bought two brand NEW so I would have a spare. Neither one worked!!! Yet I verified that one of the old relays was bad and one was good using my ohm meter. So I took the original relay(the good relay) and swapped it to the other position and it worked! Yep thats right.... I had got two bad relays from the dealer right off their shelf. The third and fourth relays I got from the dealer worked fine. Go figure.... at Ford .... "quality is job one".

So.... with all that said, shot gun approach.... try swapping the two relays with each other. If I'm right you will be able to drive the xfer case to the opposite position but not back until you replace the defective relay.

I posted a short write up back in dec '08.

 

I just tried the relay swap. No go. I have 3 little boxes, each with 2 relays apiece. I tried swapping these every which way. No good. I ran out of time again, so I haven't tested them with the multimeter yet.

 

The trick is you have to locate the right relays, these trucks have relays tucked in all over the place and in every corner of the engine compartment. On the '05 F350 PS 4X4, the Xfer case 2 relays are in a small black plastic box tucked in between the driver side battery and the inner fender.

If you are keeping the truck you can get the complete shop manual on CD from ebay for about $25, good investment.

 

I believe it. I could have had this problem solved months ago if I'd done that sooner, I'm sure.

 

There are also other posts on this issue if you use the advanced search (works sometimes). You could read all night with all the info on it in here.