Help Needed Shift on the fly not working properly

[gdf250]

Hi all. New member but not new to Superduty trucks....

I'm having trouble with getting my shift on the fly to work properly. It worked last night and I did not notice anything strange going on with the truck, nor did I abuse it. I went to put it into 4x4 this morning, the 4x4 indicator light came on, but the truck would not engage into four wheel drive. I cannot manually switch my hubs as they are locked, probably siezed....

I put the truck on a lift, switched it into 4x4 and the front shaft moves, but the front wheels did not spin. (The 4x4 indicator light came on again.)

Also, as I was driving to work, the heat was on and the air stopped blowing to the feet and automatically started blowing through the defrost vents.

Any help is greatly appreciated.

 

[AK Rover]

You have a vacuum hose busted. This was very common on these trucks when they first went to the pulse vacuum hub engagement system.

 

[gdf250]

Is there a good place to start to look? It appears the easiest place to start is at the wheels and work back.

 

[AK Rover]

I'm not that familiar with the vacuum lines and how they're routed but I would do as you mentioned and start at the wheels and work back to the motor that is mounted on the passenger side fender under the hood.

What year is your truck? The fittings at the hubs have been known to fail, espescially in cold weather.

 

[architect-builder]

As well as the seals behind the hubs. That's what my problem was. B

 

[jestersv]

done any front end work lately I would suspect seals also because it worked one day and didn't the next. If a hose leaks its not going to be intermitent.

 

[gdf250]

Thanks to all that asisted with this issue. It ened up being the solenoid on the fender. Have a Merry Christmas.

 

[benzf350]

air on on defrost

i have the same kinda problem gdf250 is having the air only comes out thru the defrost. i found a broken vacuum line at the front passenger hub. fixed it and now if i move the 4x4 switch air will come thru the vents for a a minute or so and then will switch back too the defrost. do i check for another vacuum leak?? and where are the most common places too check??

 

[gdf250]

benzf350, it ended up being the solenoid on the fender. I may be wrong, but I believe it's all tied into a master vacuum system. Before you buy a new solenoid, check out the following links. From what I've read, the solenoid is a common problem.

http://www.superdutydiesel.com/forums/search.php?searchid=423529

http://www.superdutydiesel.com/foru...ewhere-auto-4x4-how-test-vacuum-solenoid.html

http://www.superdutydiesel.com/forums/6-0l-powerstroke-engine-drivetrain/25392-4x4-not-going.html