4x4 only in manuel

[ironlemon]

Hey i just had the dealer replace both hubs with new ones. Worked 2 times, now it wont engage. If i get out and lock the hubs manuely and turn the switch then i have 4x4. The air changes temp when i tell it to and the vents change when i tell them to. Ima start by c'ing if i have vaccume at the hubs. What else do i need to check? I just switched them back to auto, and when i turned the knob on the hubs there was air pressure forced out on both of them, (where they say ford in the center of the hubs).

[skanj0]

Originally Posted by ironlemon

Hey i just had the dealer replace both hubs with new ones. Worked 2 times, now it wont engage. If i get out and lock the hubs manuely and turn the switch then i have 4x4. The air changes temp when i tell it to and the vents change when i tell them to. Ima start by c'ing if i have vaccume at the hubs. What else do i need to check? I just switched them back to auto, and when i turned the knob on the hubs there was air pressure forced out on both of them, (where they say ford in the center of the hubs).

As you mentioned, start by confirming vacuum at the back of both knuckles. Remember the vacuum is just a pulse, not a constant vacuum. Have someone in the truck turn the knob while you pull the hose off each knuckle. If no vacuum pulse at the knuckle, starting following each vacuum hose from the knuckles to the tee near the starter. Then follow from the tee upward (now a gray plastic line) to where it daylights in the engine compartment (next to the AC dryer). I found that mine had made contact with the exhaust manifold which melted and sealed the line completely. I cut out the melted portion, used a 6" piece of automotive vacuum hose as a coupler for the plastic tubing, then applied a 24" length of that aerospace looking hose/wire insulation that they sell at hot rod shops over the vertical portion of the plastic tubing (where it passes by the exhaust manifold).

Good Luck!

[ironlemon]

Hey, i just pulled the line apart, near the ac stuff and used my mouth to apply vaccum and let it stick to my lip for a few minutes, and it stayed, with no loss. So now what? Like i stated before all other hvac functions work fine.

[skanj0]

Originally Posted by ironlemon

Hey, i just pulled the line apart, near the ac stuff and used my mouth to apply vaccum and let it stick to my lip for a few minutes, and it stayed, with no loss. So now what? Like i stated before all other hvac functions work fine.

The fact that your HVAC controls work normally means that your vacuum pump is working.

The "suck test" you did doesn't really mean anything, as the plastic line could be plugged, pinched, or melted solid (as mine was) below the ac stuff. Is vacuum actually getting to the back of both knuckles? Pull the rubber hoses off one at a time and check at the back of each knuckle. If no vacuum at the knuckles, then your problem is between there and the location where you did the "suck test".

[ironlemon]

At the nuckles, doest the hose; pull off the steel nipple, or does the steel nipple unscrew. The line going down to the frame than alone the fram is ok, but thats as far as i made it.

[skanj0]

Originally Posted by ironlemon

At the nuckles, doest the hose; pull off the steel nipple, or does the steel nipple unscrew. The line going down to the frame than alone the fram is ok, but thats as far as i made it.

Yes, the rubber hoses just pull off the steel barbs on the back of the knuckles. It's usually those rubber hoses that crack, rot, and otherwise lose vacuum.

[ironlemon]

Well it was the short rubber hose on the passengers side. Now i just need some vac hose, the size i had is just a fuzz to big. Hope that was the prob.

Thanks for all the help, im still learing how everything works on this truck.