4x4 not working..?

[fishmanwill]

Well I was out hunting this weekend and went to use my four wheel drive and it did not work. I turned the switch to 4 high and the front wheels did not engage. I had to LOCK the front hubs in instead of having them in AUTO to get the four wheel drive to work. Is there a vacuum that engages the hubs in AUTO, where do I need to start checking? Thank you.

Will

[F250SixOH]

On the passenger side of the engine bay there is a vacuum solenoid. Turn your key to on and make sure the pump runs first. Then use a vacuum gauge and connect it after the solenoid to see if the solenoid works correctly when switching to 4x4. You can also check the lines to the hubs with a vacuum pump to see if one of the seals in the hubs are leaking. The vacuum solenoid tuned out to be the culprit on my truck.

[fishmanwill]

on the passenger fender wheel well? What else does the vacuum solenoid operate? Thanks,

Will

[Coach73]

would like to know the answer to that as well!! Coach

[WarChild]

Doesnt that work the AC valve on the radiator hose too?

[F250SixOH]

It controls your defroster or something like that if I remember right. If you switch to 4x4 and the only thing that blows air out is the defroster, you have a vacuum issue. Also can happen all the time if you had a leak before the solenoid I guess.

[Term3]

If your heater will only blow on defrost then you have a vacuum leak. Most of the time it's on the tubing going to the hubs. There are stainless steel braided ones you can buy but I don't recall who sells them. I just remember its a popular supplier.