Auto Lock frount Hubs

[Max2006]

My front hubs do not lock when set to auto.They work fine when I set the hubs to lock.

The truck has ESOF and the ESOF works and shifts the transfer case with no problem.

This problem has existed since new. I now have 6800 miles.

Dealer is about 100 miles away so before I make a a 200 round trip and lose use of the truck for a day or more I want to look into the cause.

Any input as to the potential cause is welcome.

Thanks

2008 F350 4X4 DRW King Ranch Job 3

[WOOL-PULLER]

maybe lost vacuum or solenoid problem

has happened a few times before on my previous trucks
common problem

[F250WHEELS]

Are you rolling when you engage FWD? It helps line things up.

[genedarrell]

i have the same issue. I was told by the dealer that there is a vac solenoid on the right side of the engine compartment around the air filter housing somewhere and he said that is almost always the problem. Have not had time to check mine out, taking it in for differential problems so while it is back stock I will have them fix that as well. Will let you know what they find.

[peteoreo]

my old one did that and when it did it was a blown 10 amp fuse

[First_Ford]

One of my trucks had an issue with it not engaging and got me stuck. I found later that the wire for the vacuum pump was off. From what I found, you can hear the pump turn on when you put the ignition to the on position ,after sitting for a while. To help isolate issue, first thing in the morning after a cold soak, put the ignition in the on position.(You should hear the pump turn on), wait for it to build vacuum pressure and turns off, this will prove nthe pump works. Then turn the 4wd high switch on, the pump should run again along with hearing the shift motor engage. wait for the pump to stop again. The pump cycle takes a while to build, just to be safe, give it 5 minutes to stop. If it doesn't stop pumping you have a leak somewhere. If it stops for the ignition being turned on and not the solenoid, there is a leak somewhere after the solenoid. If it doesn't stop after the ignition only, it is between the two. If you can't figure it out from this you will most likely need the dealer trip.

[greasltn]

If you have vacuum in the system, next thing to check is the soleonoid for the hubs. The solenoid for the hubs is located on the passenger side of the fan shroud.

[Jarrod B]

i have the issue as the op. ill check the solenoid soon.

[genedarrell]

Just got my truck back from the shop, it was the solenoid. Something that i noticed is that before I took it in my vacuum pump ran all the time, now it does not so it must have been a pretty serious leak...

[Jarrod B]

Originally Posted by First_Ford

One of my trucks had an issue with it not engaging and got me stuck. I found later that the wire for the vacuum pump was off. From what I found, you can hear the pump turn on when you put the ignition to the on position ,after sitting for a while. To help isolate issue, first thing in the morning after a cold soak, put the ignition in the on position.(You should hear the pump turn on), wait for it to build vacuum pressure and turns off, this will prove nthe pump works. Then turn the 4wd high switch on, the pump should run again along with hearing the shift motor engage. wait for the pump to stop again. The pump cycle takes a while to build, just to be safe, give it 5 minutes to stop. If it doesn't stop pumping you have a leak somewhere. If it stops for the ignition being turned on and not the solenoid, there is a leak somewhere after the solenoid. If it doesn't stop after the ignition only, it is between the two. If you can't figure it out from this you will most likely need the dealer trip.

i did that test on mine. put the key on on and the pump ran for a min or two. then turned off and didnt come back on. then put 4x4 on. pump came back on and ran for like three or four mins. went off and it didnt come back on. and i also pulled the hose off the hub on the pass side and felt no vac. so that would mean i have a leak somewhere betwen the solenoid and hubs?