ESOF 4X4 Problem?

[mazsecond]

When I put my truck into 4hi using the ESOF the 4x4 light comes on and the front driveshaft locks but the front wheels do not spin. I tried 4lo also and it doesn't work. When I lock the hubs manually the 4x4 works fine. What should I look for. I don't have any DTCs and the 4x4 lights come on and don't flash. I'm sort of stuck here. Any help is appreciated!

[NYC F-350]

Check the rubber hoses that are on the back side of the hub. Follow those all the way back to the vac pump under the hood.

[mazsecond]

Thanks. I'll check that first thing in the morning. This might be a stupid question but where exactly is the vac pump under the hood. Also, when the truck is off key on and I flip the 4x4 switch i can hear the click from what I'm guessing is the vacuum and when i start to drive I hear a little clanking noise. I've herd that noise even when the 4x4 was working., is that normal?
I think too many 4x4 launches may have and something to do with this. lol

[NYC F-350]

Vac pump is on the passenger side, between the battery and the HVAC box.
You might want to take the auto-hubs out and give them a good cleaning/greasing too.

[mazsecond]

Thanks again! I'll let you know how it goes.

[RollinEarly99]

How did it go? I currently have the same problem.

[mazsecond]

I checked all the acume lines and they all looked good they were just covered in dirt. So I soaked everything with simple green and rinsed it all off real good. Now everything works great. Some mud probably clogged up the vacume hole and wouldn't let thr hubs lock to the wheel. I should till probably take my hubs out and see how they look, maybe when I have some free time on my hands.

[Diverdan]

I have the same problem. I turn my key on, hit the esof switch and I can hear the vacuum pump running. Does it run until the hubs shift or does it run the entire time. Right now, mine runs constantly when the switch is on. I am going be pulling my tires off tomorrow and check the hoses, hopefully it is something easy and inexpensive to repair. Any lessons learned would be greatly appreciated. Thanks.

[mazsecond]

Originally Posted by Diverdan

I have the same problem. I turn my key on, hit the esof switch and I can hear the vacuum pump running. Does it run until the hubs shift or does it run the entire time. Right now, mine runs constantly when the switch is on. I am going be pulling my tires off tomorrow and check the hoses, hopefully it is something easy and inexpensive to repair. Any lessons learned would be greatly appreciated. Thanks.

I would almost guarantee that the hoses and actuator are just dirty. 95% of the time thats the problem. Clean it out real good as I described above and that should fix your problem. When I took my hubs off their was a ton of dirt and crap caked on them from off roading. If your pump is running and the transfer case is engaging theirs really nothing else that can go wrong.

[Diverdan]

Thanks for the advice. I am going to do that, just pull it apart and clean it all up. Should my vacuum pump run the entire time the switch is turned on? At work when we need to find a vacuum leak, we use shaving cream, think I'll try that too, just to make sure none of my hoses have a leak.