4WD Weird But True

[brian42]

I need help! I just bought a 2003 7.3 4x4. Every time I shift into 4wd my ventilation blend door switches to defrost. I don't have a shop manual yet and have no idea where these systems could possibly affect each other. I thought it was weird when it happened and maybe some freak coincidence, but it's not.

I like to consider myself fairly handy with a wrench but this one baffles me. I have no idea where to even start.

[wetco416]

Brian you have a vacuum leak in your system somewhere,you can start your search at the front hubs,right behind the tire is where the vacuum line goes into the hub and that is where it will probably be wore out and cracked,just cut a little off and reattach.if thats is not it keep searching

[Dave]

Originally Posted by brian42

I need help! I just bought a 2003 7.3 4x4. Every time I shift into 4wd my ventilation blend door switches to defrost. I don't have a shop manual yet and have no idea where these systems could possibly affect each other. I thought it was weird when it happened and maybe some freak coincidence, but it's not.

I like to consider myself fairly handy with a wrench but this one baffles me. I have no idea where to even start.

The same vacuum system controls the vents and the 4x4 auto hubs. most likely the problem is the rubber seal on the hub is shot

[worx]

If you want a DVD version, grab it from here...
Ford Repair Manual CD/CDs/DVD/DVDs Service Manuals
maybe the service manual will help... I gotta go find where my dvd went to...

[sjp649]

Mine is doing the same. I changed all my vacuum lines and the nipple that the hose attaches to in the hub. Still did not work. Found out that the hub solenoid is shot(vacuum motor) It is on the right front fenderwell right next to the vacuum canister. Turn your switch on, and feel if the motor runs, it should stay on for about 45 sec.

[Albie30]

Ditto I ve got the same problem and I thought the same thing when it happen to me

[matts7.3]

If it will only stay into defrost mode while 4x4 then you got a leak in the lines or hubs after the solenoid. If it stays in defrost mode even when you are out of 4x4 then your solenoid or vaccum motor is shot. A new solenoid is around $40 through the dealership. If its the hubs you may want to think about switching to some manual warn hubs. Wont have to worry that your stock hubs slip out of 4x4 if it leaks again.