I know much has been posted on ESOF and electronic transfers case shifting issues, but I had a recent experience that was a little different than most and thought I would post what happened.

Quick background: I have a 2003 F250SD Extended Cab V10...US truck now living in far eastern Canada where it is well-versed in wintery weather. The ESOF works as it should...switching between 2wd and 4Hi is normally uneventful...the vacuum end of the system is not an issue at present - I had the whole front end repaired about a year ago when it was acting up. On the few times I have engaged 4Low, I have had the sometimes back the truck up to get it to change back to 4Hi or 2wd, but I have never had an issue with it not shifting.

Recently, my son switched the truck inadvertently into 4Low and drove it there for a while (he did not know the procedure to get it back to 4Hi). When I noticed this, I did attempt to shift it back, but found the transfer case stuck in the neutral position - transmission will engage, but the truck would not move in either direction. The dash indicator lights were not lit (usually meaning you are in 2wd), but clearly I was in transfer case shifting no man's land...or the transfer case was toasted. Note that I did not pull the codes from the computer...I don't have that capability and the truck was not mobile to get it done elsewhere.

With info from this forum and some googling, I started to diagnose the situation....fuses were all fine, the transfer shift relays were clean and benched tested fine (swapped positions as well), the mode selector switch ohmed out fine. The I figured the issue was the case shift motor. Seeing it was cold and snowing outside, I wanted to determine this before getting under the vehicle. At this point, the dash indicator was out and moving the MSS produced no relay or motor activity. With the transfer shift wiring diagram, I figured out how to jump the two shift relays (with key off, jump 87 & 30 on one relay and 87A & 30 on the other) and the motor moved. Reversing the jumper setup between relays moved it the other way (sounded that way anyway). In both cases, the motor turned for a very brief time...maybe 1/2-1 sec. I picked a direction to turn the motor, reinstalled the relays, started the truck (MSS was in the 2wd position at this point and the dash indicator was still off) and...success! The transfer case was engaged and the truck now moved. It was in 4Hi, but on a quick test drive, the electronics figured out that I wanted 2wd (the MSS position at the time) and changed to 2wd. Subsequent tests proved I could change between 2wd and 4Hi with no issue...did it maybe 5-6 times over a period of about 20 mins.

At this point, I tried shifting to 4Low from 4Hi (dash indicated showed "4x4" at this point)... but no joy. The dash indicator did go out, however....but the truck remained in 4Hi. After that point, I could not shift the transfer case at all. I did a key on/engine off transfer mode test and found no activity on the shift motor or relays. I surmised that the electronics could not figure out what state the transfer case was in, so it did nothing. I attempted my manual relay manipulation again to see if I could "move things" to get them working, but no go this time. At this point dark and cold overtook, so I retreated to think about things for a while.

All things are pointing to a wonky case shift motor...I figure it's weak with age or the mode feedback mechanism in it is sticky or toast. Maybe it’s just the cold weather. I was wondering if there is a way to figure out what relay jumping sequence moves the shift motor a specific direction. If anyone knows how to do this or recalls what they connected where when bench testing the shift motor out of the truck, this would help. MY idea to try to move the motor clockwise (to 2wd or 4Hi position) and see if things start working normally again. I know I can probably do the same thing by removing the motor, bench testing it and directly shifting the transfer case, but if I could do it from under the hood…well, so much the better. Or maybe I should just replace the shift motor outright? All ideas welcomed.

Regards,
SteveCo in St. John’s

 

Subscribed. Interested in any words of wisdom.

 

Just though I would close the loop on this one, in case someone wanders down the same path I did. After my original post, I purchased a new t-case shift motor (Dorman PN: 600-805...widely available and about $150+tax). I found a post on another forum that gave a good overview of the replacement process, but I did notice a few details along the way. If you have diagnosed the shift system and have determined that the t-case shift motor is the errant component, here are the basic steps to replace it:

1. If the 4WD shift system is still operable, put the truck in 4Hi (more on this later). Apply the park brake and block the wheels.
2. Remove t-case skid plate (four 10mm head bolts).
3. Remove the two wiring harness connectors:
- Shift motor connection: depress the tab and pull/wiggle it off towards the passenger side.
- Shift position feedback connection: Slide the red locking tab towards the driver's side, all the way to the end of the connector. Depress the locking tab exposed under the red tab (a screw driver helps with this). Pull/wiggle the connector off. This one needed a bit of persuasion with a wide-blade flat screwdriver to get it moving.
4. The shift motor is held in place by three 10mm head bolts with blue Loctite on the threads. Take care removing them as you can easily shear off the bolts. See more below.
5. Remove the old shift motor. Clean the mounting face on the transfer case and t-case shift extension and put a small amount of lithium grease on the shift extension only.
6. The new shift motor comes set in the 4Hi position. If your t-case is not in this position, use a 14mm open-end or adjustable wrench to move the t-case into the correct position. The t-case shifts from 4Lo to N to 4Hi to 2WD clockwise (looking at the shift extension from the driver's side).
7. Apply a small amount of lithium grease to the o-ring and shift socket on the new shift motor. Apply some RTV gasket maker on the t-case where it mates with the shift motor. This is more important if there is significant corrosion on the t-case from the old shift motor, but it's a good idea anyway. Avoid getting the RTV on the o-ring area.
8. Mount the new motor. You may have to twist the motor a bit to line up the mounting holes with those in the t-case. You will in fact move the shift motor or the t-case shift extension while doing this.
9. Snug the bolts up and torque as per the vendor's specs. In my case this was 15ft-lbs (20MNM).
10. Reattach the electrical connectors...remember to slide the red tab closed.
11. Test the shift mechanism. If OK, reinstall the skid plate.

A few observations from my experience:

I did not heat the bolts before removal and this was a mistake. I twisted off the head of the bottom bolt trying to remove it, leaving about a 3/4" of the bolt sticking out of the t-case. I suspect that bolt was seized to the shift motor case mounting hole (there was significant galvanic corrosion on the exposes threads of the bolt). Luckily, I was able to heat the exposed "stud" and thread area and remove it with a stud remover without incident.

I recommend whacking the bolt heads to break any corrosion free and heating all the bolts before removing them...I used a simple butane torch and moderate heat. Some online research indicated that only 300-400F is needed to soften the Loctite. The upper two mounting bolts are harder to get at, but it is worth the effort. My errant stud released easily when this was done, but if the bolt had sheared off at the surface, I would have had to remove the t-case to extract it (rear drive shaft yoke is in the way to fix it in place).

You can decide whether to reapply blue loctite to the bolts, but I think it's a good idea. I reused the old bolts (well 2 anyway) but ran the bolts thru a through a die to clean up the threads before reinstalling. I applied some anti-seize to the mounting holes in the new shift motor to prevent galvanic corrosion between it and the bolts.

I found the two electrical connectors hard to get off and the plastic was a bit "crisp". Care had to be taken not to damage the connectors. The terminals inside with perfectly clean, but a dab of di-electric grease would not be a bad idea before re-assembly.

When testing my new shift motor, I found it shifted from 4Hi (the install position) to 2WD mode perfectly, but would not shift back to either 4WD mode. Swapping the shift relays allowed me to shift to 4Hi/4Lo, but not back to 2WD. Clearly one of my shift relays was toast. I had tested both as part of the diagnostic process, so I suspect one of the relays burnt out when the old shift motor packed it in. The PN on the relay is: FOAB-14B192-AA. I understand this is a basic "Bosch" style 30amp relay...available widely and the Ford part is not required. I replaced mine and the system worked as it should. Mission accomplished!

That's it for this one. Hope some of this is helpful. Let me know if you have questions or need more info.

Regards,
SteveCo in St. John's

 

I know this is an old post but thanks for the notes.
I also read that some of the earlier 99-02 trucks had a GEM module behind the fuse panel that can cause problems with the 4WD system.
If you get this note did replacing the motor and swapping the relays work. Connections seemed clean and sprayed with some electrical contact cleaner.
I put new relays in my truck tonight but no shift in or out of 4WD.
It seems intermittent as it was working last week fine.

 

Replacing the transfer case shift motor fixed the problem. There was something wrong with the old shift motor...it was the original unit and I live in a salt-rich winter climate. It was not hard to swap out, but did require the transfer case skid plate to be removed (on my FX4 model) and I did break off one of the shift motor retaining bolts (there were 3 IIRC) in the process. I was able to get it out will a little heat and a pair of vice grips. The bolts have blue thread locker on them, so it might be worth being aware of this before you start...they are fairly small bolts (6mm with a 10mm hex head, I believe) and it does not take alot of torque to break them.

A good test of the electrical part of the system is to pull the plug on the shift motor and attach a test light to the contacts (there are just 2 IIRC). If the test light lights when you operate the 4x4 selection **** (it's a series of pulses or duration of signal I am lead to believe), then chances are the problem is your shift motor (ie: electrical is fine, so motor must be bad). If not, then you will have to work your way up the wiring harness to the relays and on to the the selector **** or the GEM. I did not have to go that far, thankfully, and suspect you would have other systems not working if the GEM was bad.

Ironically, as I write this post, my truck is again stuck in 4wd High. This time it is a bad "shift back" relay and I was able to get the truck to shift out of 4wd by swapping the relays in place. For a week or so the selector worked fine again. Sadly it was not to last and the truck is stuck in 4wd high now....time for a new relay or two!

Good luck and let us know how you make out.

Regards,
SteveCo

 

Thanks SteveCo, your post above was just what I needed to position my transfer case and finish up my shift motor install. Cheers man!

 

Glad it was helpful!

 

”6. The new shift motor comes set in the 4Hi position. If your t-case is not in this position, use a 14mm open-end or adjustable wrench to move the t-case into the correct position. The t-case shifts from 4Lo to N to 4Hi to 2WD clockwise (looking at the shift extension from the driver's side)”

Do you have anymore details on this? My transfer case is stuck in 4L and when I go to install the new shift motor, I’m unable to get it into 4hi. The shaft turns just fine, but doesn’t lock into the next position and springs back. Hoping this isn’t a sign that my t-case is jammed up and I’m just missing something silly. TYIA!

 

Sadly, I don't. I was able to use the 14mm open end wrench and shift the t-case to match the new motor position. It was a while back when I did this, but I recall it was not really easy to manually shift it...but was not super hard either. A decently long wrench should move it with modest effort, but I don't recall any spring back or thinking I was going to break something, IIRC, the transmission was in Park when I did this, but you might try putting it in neutral. The truck won't shift for 4WL to 4WH unless it's in neutral under normal circumstances...but I believe that is an electronic lockout, not a mechanical one. That said, it would likely be easier to shift if the trans is in neutral in any case. Just make sure you block the wheels before crawling under the vehicle to try this!

Regards,
SteveCo