Need to repair my auto 4X4....

[Sesco4]

With winter right around the corner I need to fix my auto hubs. Here's what's going on. When I flip the switch on the dash to go into 4wd it don't work. I know I have a vacuum leak cause when I flip the switch with the a/c or heat on it starts blowing out the defrost. So where is the best place to start looking to track down my problem.

Thanks

[Davey~do]

#1) Check the hoses where they fit to the axles. They are pretty notorious for cracking there. Pull the hose if it isnt obvious; try the 4WD command. If it stays blowing as it should there's your problem.
#2) Vacuum Solenoid

[Sesco4]

Well I finally got a chance to crawl under the truck and take a look. Turns out that both hoses we're cracked at the nipple on the back of the wheel. Hopefully this will get everything back to normal.

[duc796]

Did your 4 wheel drive light come on when it wasnt working when you switched to 4wd? I lost my 4wd yesterday at the track. Im thinking its electrical since the light doesnt even come on. Fuse is good trying to figure out where to look next.

[NYC F-350]

ESOF (electronic shift on the fly) system file attached. Has all the pinpoint tests you will need to diagnose any issue.

[duc796]

This should help out a lot thanks!!

[Sesco4]

My 4X4 light always comes on. I thought I might have fixed my problem with finding the cracked hoses going into the back of the hub. I needed to use my 4wd this past weekend and to my surprise no 4wd at the flip of a switch. I rolled the truck backward a little hoping that would help lock it in but it didn't help. So I'm still without the auto 4x4.

[NYC F-350]

See post #5, download the PDF file and start digging in.

[duc796]

Im thinking mine is somthing electrical. I checked both the fuses for the 4wd theres a 15A under the dash and a 30A under the hood. Im leaning towards the solenoid on the transfer case since Im getting no light or anything with it.

[Sesco4]

So after donig a little investigating I've narrowed it down to the drivers side hub. I pulled both hoses off at the hubs and blocked them off. A/C kept blowing through the vents. Then left pass. side hooked up and blocked the drivers side with the same results. Lastly left the drivers side hooked up and pulled the pass. side and blocked it off and the A/C went from vents to defrost. So now what is there an o-ring that I need to replace or the entire hub or what.

Thanks