Hi to all and thanks for your response,
I have a 1999 F-350, auto, V-10 with Auto/Lock hubs and shift-on-the-fly (ESOF). When I activate the ESOF the lights on the dash cluster do not light and there is no transfercase engagment when in either Auto or Manual hub lock.
There is power to the #1 relay and I replaced the same, the GEM fuse was pulled to reset it, there is power to the ESOF switch. I know that the 4wd cluster lights work, because I see turn on everytime I start the truck.

THERE IS NO POWER TO THE TRANSFERCASE MOTOR?????
Does the vacuum to the hubs and the hub lock solenoid have to activate 1st, before the 4wd lights come on and before there is power to the transfercase motor.
What fuse and relay is for the Pulse Vacuum Hub Lock Solenoid.
Thanks, John

 

Well i hate to say it i might be wrong on this one but ill give it a go its possible your trasfercase motor is shot does happen...

 

I'm pretty sure that the transfer case engagement and the vacuum solenoid are unrelated and it will in fact kick in the transfer case with a shot vacuum solenoid.

The 4x4 light will only come on when the transfer case is locked in. The hubs don't even factor in that.

It could well be the 4x4 motor. I imagine that there is a position sensor on there, too. That could be feeding crap data to the module and messing the whole system up, but my bet there is that it's integrated onto the motor kind of like the wiper park switch is on a wiper motor.

 

How did you test the power to the shift motor? Which wires and how did you activate the control module? Was it within 6 seconds of activating it?

 

How do you know if the Vacuum hub lock solenoid is working (Where is it's relay and fuse??)
I had someone switch the ESOF while having a test light on the wire going to the shift motor.. I don't know if I waited a whole 6 seconds. We did this with a test light and found power to the #1 relay and the ESOF switch itself.

 

Did you have two wires going to you shift motor and test each one independantly and ground your test light to the vehicle? Check under your dash number 25 4wabs and 28 hublock solenoid and 17 esof motor under the hood (start here) and 40 esof relay 1 and 2 When you say the number one relay do you mean under the dash? That is the flasher for your lights. Do you have your manual to see the fuse numbers? Dont worry about the Vacuum Hub Lock Solenoid they are unrelated at this point.

 

OK, here's the deal. First off, thanks for for looking at my concern, I do really appreciate any help and suggestions

2nd, today I examined the pulse vacuum hub lock solenoid and the vacuum lines going to each hub. Visual inspection all looks good, did not see anything unplugged or cracked. Also I learned that if the A/C & defroster do not vent properly that there is a vacuum leak somewhere (including the hubs) since they share the same vacuum as the hub solenoid.

3rd. I inspected the underdash fuse box, I already replaced the #1 replay, the #2 relay is left out due to my application. #15 fuse GEM Powertrain and #19 GEM Module and #28 ESOF fuses are good.

4th, Underhood fuse #17 ESOF & Transfercase motor is good.

Now the underhood fuse box digram within my manual says Fuse/Relay #40 (ESOF Relay #1) The highest # under the hood goes to 37.
I have no #1 relay under the hood, I assume it is mentioning the #1 relay under the dash???? When I read the diagarm again for under the dash it says #1 relay interior lamp relay????? What is correct!!!!!!!!!
Shouldn't the transfercase engage when I switch to LOCK on the hubs. Doesn't that by-pass the vacuum. But then again how does the transfer case engage w/o the ESOF.
I look farward to any sugestions.
John
Harrison, Arkansas
1999 F-350 V-10, Auto, Crewcab dually.

 

When you turn that switch to a 4x4 mode, the control module energizes the vacuum solenoid to send vacuum to the front hubs. It also sends the command to move the transfer case motor so the transfer case is put in the right position.

Locking the hubs engages the front axle, which will spin everything up to the front drive shaft going into the transfer case. You won't actually have torque being transferred to that front shaft until the transfer case motor moves the transfer case's mode fork into 4x4.

On the manual system, the driver gets out and locks the hubs. Then you pull the lever on the floor into 4H to engage the transfer case. Basically, the ESOF system is doing the same thing by remote control, and it's two separate processes. If your vacuum went kaput, your 4x4 would still work if you went out there and manually locked the hubs in. If it does not, then the transfer case is not going in.

I suppose that you could actually check if the transfer case was engaging by plugging the vacuum lines to both hubs and making sure they were in the unlocked position. Then you could put it in 4x4 and get someone to carefully watch underneath and to see if the front shaft turned. If the hubs aren't in and that front drive shaft moves, there's only one thing that can do it.

 

Hey Cowboy,
Thanks for the reply and info.

If I do what you say and the hubs aren't in and the shaft moves, what is the one thing that can do that?????

Does that mean the GEM or the Vacuum hub lock solenoid is bad.
And if still no 4x4 lights on the dash, then what?

Thanks in advance, John
Harrison, Arkansas

1999 F-350 V10 Auto Crewcab LWB Dually