2000 f350 ESOF problems: hubs wont engage

[ryan10]

hi, i have a 2000 f350. Last winter the 4x4 worked great. I went to try it this year and nothing. when i lock the hubs manually, it will go into 4x4 fine. However, on auto the hubs do not lock. i have been working on it, and when i flip the switch from 2wd to 4x4, the pump on the drivers side fender well goes on, and i have vacuum going into the PVH solenoid, as well as coming out of it. I also have vacuum at the spindles. When in the cab, when you switch from 2wd to 4x4 the heater settings will default to defrost. I have looked for a vacuum leak and cannot find anything What else should i check for?
thanks

[Young-SC-Owner]

The hubs are leaking internally.

Get rid of the autolockers and alot of hassle and get a good set of WARN manual lockers.

[ToMang07]

Welcome to guzzle's 4x4 Autolock Hub Lubrication Maintenance Web Page

[late_99_PSD]

Its probably the vacuum seal behind the bearing. It was a while ago when I replaced mine but I don't think they were too much work to replace. I forget how much they were but I got new seals at napa when I did my ball joints and they work great now.

I love my auto hubs. A little maintenance goes a long way to keep these operating like they should.

[Fade 2 Black]

Mine need to be completely rebuilt. The main vacuum stub shaft seal is shot and the stub axles are worn and grooved where they ride on the needle bearing inside the hubs. I got it used so there's no telling how long they've been like this.