I have a '99 250SD with ESOF, (first ESOF,learning a lot on this site) if the vacuum hubs go bad, will the "4X4" light on the dash still come on, or is it only activated after the hubs engage? Still original hubs (going to switch to Warns), turn the switch on the dash and nothing, no lights(light does come on during start up), no noises, no 4X4, no voltage at switch or at motor on transfer case. 30 amp fuse under hood is good, voltage on both sides. Is there a troubleshooting chart available somewhere to diagnose this problem?

 

The dash indicator represents the position of the transfer case motor only, the is no indication of operation of the hub vacuum.

Check voltages at the connector of the trannsfer case motor.

If you remove the motor you can also apply 12v to it to the pins to check the movement of the motor.

With the motor off truck, you can crank the transfer case with a socket wrench (3/8 square drive I think) to selection of the 4x4 (2wd-4HI-4LO) and this should light the dash light (with ignition key turned part on).

Be sure to mark the position of the crank nub and the motor spindle BEFORE you play with it so you can put the motor back on afterwards!

On my 2000 F250 I found the motor was powered and turning but the plastic worm gear inside had stripped, so it was making the noise of moving but not actually turning tha transfer case nub.

 

...Welcome to Ford Truck Enthusiasts!

…..See you on the boards.

 

Make sure that you read the manual and follow it. I know the "Shift on the Fly" means that you can do that - and there's no problem there, unless you switch directly to 4LOW. ESOF is for 4WD High only.

Back to the problem: Other than what Musicman250 said, which is good info, btw, you also need to know that if the system has not been energized in awhile, it will be stubborn. Make sure you're on level ground and follow the 4WD Low instructions even if you are just switching to 4WD High. I say that because you sometimes need to exercise the system. Be patient - allow the relays time to work. Listen for the "switching" sounds if possible; you might need help for that, but it's necessary to find out if the servo motor is getting power.

Check back with us and let us know what you've done.

 

Had the truck up on the hoist at work, front hubs seem to be locked (front axles turning with tires) no markings on the hubs & they (hubs) won't turn at all. I have no voltage at the switch in the dash with the key at any position.
Also no voltage at the transfer case motor with the key at all positions and the 4x4 selector switch on the dash at any positions.
Where is the next place along the system to check for power supply?
The 30 amp fuse in the power distribution box under the hood/on the fenderwell is hot, voltage on both sides.
Check the relays next to the mastercylinder???? which points should be "hot" to feed the relays??

 

Without getting too complicated: The GEM (Generic Electronic Module) controls the power to the relays. Check the GEM first.
Don't know what engine you have, but here's a location for the GEM
http://dieselinnovations.com/techfil...4_location.pdf

Also the 99 models had a recall on the GEM:
Ford Motor Company is providing a no-charge Service Program, Number 98B29, to owners of certain 1999 Model Year F-250/350 4x4 Super Duty series Trucks.

REASON FOR THIS PROGRAM

The Electronic Shift On the Fly (ESOF) 4x4 system may become inoperable. In some cases it may also shift from 4x2 into 4x4 with no input from the driver. This condition may be the result of GEM (Generic Electronic Module) system software concerns.

Let us know what you come up with.

 

I pulled the transfer case motor off today and ran 12 volts directly to the motor and nothing, dead to the world. Pulled the cover off of the motor and it looked horrible, all corroded and full of sand-like crap, tried to clean it up~still nothing. Pulled the motor apart and the windings were trashed. Is there any way to purchase just the electric motor seperately? Dealership lists the transfer case motor @ $502. Think I'll look for a used or aftermarket one if available.
I did manually shift the transfer case into 4X4 Hi, 4wd works which is good because we just got about 4-5 inches of snow.

 

I replaced my TX motor with a refurbished one from my local Alberta Driveline, Canada. It cost $250 Canadian then got a $50 refund for for returning the old motor. This included all shipping from his supplier somewhere in the States.