Sound like a hub problem to me. If the transfer case was still locked in 4x4 the front driveshaft would not turn. I would jack up the front end, spin the front wheels and check if the hubs are still locked.

 

Thanks for the advice, however, maybe I'm not explaining it clearly, when the transfer case drops out of 4wd into 2wd while driving in the snow I can spin the rear wheels & then I stop to check & the hubs are still locked & the 4x4 light is still on. I know the hubs are locked because I can't turn the driveshaft, however only the rear wheels spin. If I flip the switch to 2wd & then back to 4wd the transfer re-engages.

 

I guess my first question to you would be how do you know you are dropping out of 4WD? If the hubs are still locked and the 4X4 light stays on, what is telling you that your truck isn't in 4 wheel drive?

 

The rear wheels spin and the front don't!

When the sun comes up I will check to see if the front drive shaft is rotating while the rear wheels are spinning, this will help verify if it is the hubs or the transfer.

 

Try turning the Auto/Lock hubs to the lock posistion,,,see if it stays in 4x4 that way,,,if so you,,you may have a vacum hose problem etc.

 

I stand corrected, it is a lockout/hub issue, the left one is unlocking, and it will re-lock as soon as I flip the switch. I also noticed that when it unlocks, if I spin the tires in reverse it will re-lock with a loud clunk. It is frooze-up & I can't manually turn it to the lock position so I will buy a new one & go from there.

Does this make sense to anyone?

Would a vacum leak cause it to unlock after it's already locked?

Thanks FTE for the responses and the loads of info I have found on this forum

 

A vacuum leak would make it unlock after it was locked. After you buy a new one you may still have a vacuum leak to find. You will at least be able to put the hub in the lock position though.

 

So the vacum is on the lockout constantly while in 4x4?

I also noticed after it unlocks, if I spin the rear wheels in reverse it will lock back in with a loud clunk, then put it in drive and away we go. To me this doesn't sound like a vacum leak, however I've been wrong before......

Also I don't have the typical heater/defrost issue associated with a vacum leak.....or does that only happen with a large leak?

Thanks again for the help!

 

It is not constant vacuum. A few seconds to engage then a few seconds to dis-engage.

Just a guess but it does seem like the hub is damaged somehow popping into engage/dis-engage.

Rick...

 

This is how the hub operation is described in the Ford WSM: The Super Duty and Excursion 4X4 ESOF system uses timed vacuum sequences to lock and unlock the wheel ends. A high vacuum level is used to engage the hublocks, and a lower vacuum level is used to disengage the hublocks, after which the vacuum is released and the hublock holds itself in the proper mode. The vacuum signals are supplied to the hublocks by system components, including the GEM, wring harness, solenoid, vacuum harness and vacuum seals. As the first step in service, eliminate such obvious items as loose wiring connectings, loose vacuum connections, or damaged vacuum lines.

 

I just talked to the dealer & they will have one tomorrow, I will report back on the result!

Thanks,

 

You have only ONE hub that is coming unlocked. That's why you can't turn the axle by hand.

There is a latching mechanism in the hub, and if that breaks, it won't stay locked after the initial vacuum pulse which lasts 40 seconds.

I had this happen to my 2001, so instead of buying a complete new hub, I replaced them both with Warns. No problems now

 

My truck is doing the same thing. I'll have to jack it up and check the hublocks, but I recently replaced all my ball joints and got all new seals, o-rings and hub assemblies so I didn't even consider it to be a hub problem.

I don't understand how one hub not locking will cause it to go in and out of 4wd. When I engage mine all my wheels claw for their lives in the sand, but after awhile without using the 4wd too hard, I'll get back on it in a soft section and my rear wheels spin. A quick click to 2wd and back to 4wd and my front wheels are clawing away again. All the time my 4x4 light is on (except when I select 2wd). I've been trying to chase it down, but it is starting to do it a lot now and I'm sure it's not great on the t-case to keep cycling it like that.

 

I got the new lock-out/hub today, installed it in the parking lot at the Ford store, flipped the switch to 4x4 & away we went on the snow covered streets. After 30 miles of city streets & country roads she never un-locked once, She's fixed! I know I could have bought a set of after market lock-outs for the cost of one oem, but I'm lazy & it sure is nice to just flip the switch & not have to get out to lock in the hubs.

Thanks for the help!

Jeff