4 WHEEL DRIVE NOT WORKING
 

I have a 07 F350 diesel, 4wd not working:

#1 have 12 inches of vacuum at the output of the pump AND the solenoid going to the front hubs, is this enough vacuum to fully engage the hubs?

#2 I found that the inside seal on the drivers side is not completely seated,( pump does not shut off) and I can't create any vacuum (manually) directly from the hub like I can the other side.

I plugged that line ( bad side - pump shuts off) , engaged 4wd thinking I would get power to the other side ( good side) , but I did not ,,,,,,I'm thinking either 12 inches of vacuum is not enough or possibly it is, and being that the front axle is not ''POSI TRACTION'' (probably not) the differential can't/won't push power to the good side ???. Any help is greatly appreciated, especially if you know for sure the designated vacuum amount from ''out of the box condition'' ?

Also the heater has been defaulting to the defroster, if I shift the 4wd into 4 WD or out of 4WD the heater will go where it is suppose to.,,,,i.e. vent or floor mode,,,,,Thanks for any help, DON

I don't recall the exact numbers, but 12in sounds reasonable. Also, it sounds like you found where your leak is and that would cause the defroster problem you mentioned.

No, your front diff is not "posi trac"/limited slip/locked/etc unless someone put an aftermarket unit in.

Have you tried just turning the hubs to LOCK manually? That should get your 4x4 working until you get a chance to fix your vacuum leak.

4 WD not working
 

Locking the hubs manually does work but i figured if i plugged the bad line i would get 4wd on the fly to the good axle without locking the hubs in,,,,,but that is not working.

I'm not an ESOF person, I have manual. :-D From what I understand the vacuum will pulse for 45 seconds to lock the hubs and 15 seconds to disengage the hubs. 10 or higher is sufficient to lock and unlock the hubs.

Lock both hubs manually if you have to, one on and one off is not a good idea.

Yeah, that won't work. Even if you did have a locker up front, like Maxium4x4 said, it would be a bad idea to run like that.

I plowed with the hubs manually locked and did fine, don't know if both hubs had power or not but figured plugging the line would cure the problem, at least to get the shift on the fly working, at least to one wheel. However I'm not sure the vacuum control solenoid is doing it's job. With everything hooked up the heater defaults to the defrosters, if I activate the 4wd, the heater will act as it should. I'm wondering if there is another componet that is preventing the correct electrical charge from being sent to the solenoid. There is one plug with 3 terminals....
Sorry for the late response, had to run out, back now. pulling my hair out,,,,

Sounds like your solenoid is leaking vacuum if the pump runs constantly. In your other thread asking about aftermarket vacuum solenoids, I doubt it.