I have a 2000 f150 extended cab 4x4 with ESOF. To start, I just changed the pass side exhaust manifold gaskets, due to an exhaust leak. While reinstalling the inner fender I pushed the vacuum lines for the 4x4 accuator against the hot manifold and melted them in two. I trimmed and spliced them back together and tried it out. No 4wd. To make it more confusing, I have had an intermittant problem with the truck not shifting into 4wd for several months, but had sort of forgotten about it, cause I haven't needed it this summer. So here's the facts:
-All the vacuum lines hold vacuum (testing with a hand vacuum pump)
-The vacuum from the intake is 22. Vacuum at the resovoir behind the battery box is 19. And at the line that goes from the resovoir to the solenoids its about 12.
-Both solenoids bench tested ok. The 2wd solenoid doesn't hold vacuum great (maybe a small crack in the body) but both of them open and close when actuated with 12volts from a battery charger.
-The pink (2wd) line always has vacuum, regardless of dash selector switch position, and the blue line(4wd) never does. So the solenoids (that seem to work on the bench) are not switching when 4h is selected.
-The actuator at the front axle works fine when vacuum is applied manually, and the front drive shaft does engage and disengage accordingly.
-When I switch from 2wd to 4h I hear a click up in the dash (which is normal), then a pause and about 6 more clicks (which is not normal) and then nothing. The 4x4 light on dash does not come on, but does work. I see it flash when I turn the ignition on.
-When switching from 2wd to 4h I feel no clicking at the solenoids.
-Fuse 23 was fine, but I switched it out just in case.


So alot of the individual parts seem to work. I have not done anything with the actual dash switch. Is there a procedure for testing it??

Also, I read about a poster that had similar problems and it turned out to be what he called a transmission range sensor switch. He said it was located on the front left side of transfer case. He had a msof system, and either the esof doesnt have this or I can't find it. Anybody know anything about this???

I don't know how to tell if the motor on the back of the transfer case is working. Thinking that maybe if it doesnt engage, then maybe the solenoids dont get the signal to provide vacuum to the 4wd side of the acuator. I did tap on it with a hammer while changing from 2wd to 4h to see if that would help break free. If its not working. Anyone know how to check this part for correct operation??

This thing is really kickin my butt, and any info, ideas or advice would be greatly appreciated. Thanks, Diggler

 

When you unplug the vac lines from the front diff actuator, you can engage the differential shift fork manually...

When doing so does the passenger front axle shaft engage?

Connected to the shift fork is a thrust collar that slides over the splined axle shaft... This locks the passenger side axle to the diff... The Teflon bushings can crack away causing an intermittent issue and ultimately a non functioning 4x4 system...

 

Yes I can move the actuator back and forth (with some effort) manually with the vac lines disconnected. The only difference I see tho, is that the drive shaft from the transfer case then turns when I roll the front wheels. Both of my front axle shafts turn with the wheels regardless of the position of the actuator. I assumed that this how it is supposed to work, is that not right. Ive seen some stuff written up about newer trucks having "actuators" at the hubs, but mine doesnt have anything at the hubs except brake line and wheel speed sensor.

 

With the actuator in the unlocked position, transfer case disengaged, you should be able to spin the drivers wheel and the passenger wheel will not move, the drive shaft will not move either, if it does there is a problem with the collar/shift fork/passenger axle shaft...

With it locked, transfer case disengaged, you will spin the drivers wheel and the passengers wheel will spin along with the drive shaft...

 

Also there are no other engage/disengage components out at the hubs

 

Here is a video I took off my front 8.8 to show what spins when the fork is disengaged... (The first 2 seconds are the whole video, no need to watch the whole thing)

The only thing that will move is the spider gears when turning the drivers side axle... Not the ring and pinion, not the outer passenger axle, therefore, the drive shaft won't spin nor will the passenger side wheel, the spiders just roll and mesh spinning the inner half of the passenger axle freely... Once the fork is engaged, it thrusts the collar over the splined 2 piece passenger shaft locking it as one over to the wheel thus tying the two sides together in turn rolling the carrier, ring and pinion and drive shaft...

https://www.youtube.com/watch?v=Vzdw...e_gdata_player

 

Here is my shift fork I gave to another member on here cuz his bushings (the 2 white pieces on either side of the fork) disintegrated...

 

Here in the members photo I gave the fork to, you can see the 2 piece splined axle shaft where the collar which is splined inside would slip over both sides of the axles splines bridging the 2 shafts together making one, which ties everything together...



Sorry if this is a bit much, just trying to help out haha...

 

Turned out to be the transfer case shift motor, but thank you for all the good info. Diggler

 

Awesome! Glad you found it!