4 wheel drive gremlin?

[white7wolf]

So ive had something weird happen. I got my expy back in December /January and at the time the 4 wheel drive did not work. Going from 2wd to a4wd just cause the light to blink (it's a 98). 4x4 and 4lo would light solid and the transfer case engage but the front hubs would not.

Anyways i was playing with settings today and everything is working now! The hubs are engaging and the a4wd now lights solid. Any body have some in sight into maybe why this would happen?
My father in law was thinking maybe since it was 85 degrees out fluids thinned out? Im not even sure how things are setup?

Thoughts? Opinions? Bad jokes?

Thanks!

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[Canadian Expy]

The front locks using vacumn so you might want to insure you don't have a vacum leak. Also check the wiring at the transfer case. Unplug it and make sure its clean and dry.

 

[toms89]

The front hubs themselves cannot unlock on the 1st gen expys. There is a center axle disconnect on the 97 & 98's that effectively "disconnects" the front drivetrain from the transfer case. It is vacuum actuated as CanadianExpy said.

Should be just to the left of the differential as you view the front axle from the front.

 

[white7wolf]

Hhmm ok but what would make it start working now all of a sudden? If it was vacuum related wouldnt it be an issue year round?
Is there a solenoid or something that could have been bound up?

Thanks

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[toms89]

Here is a exploded view that shows the internal workings of the center axle disconnect. The vacuum control for it is #10 in the photo. I believe others have had issues with the center axle disconnect before but have no first hand experience with it.

 

[tonydiv]

The lever that goes in to the diff to actuate the center axle disconnect (# 24 - 25 above) will sometimes stick. It's a steel piece going in to an aluminium housing. Mine needed to be loosened up with a pair of channel locks and a can of WD40.

It could also be that the vacuum solenoid that activated the system could be on its way out and didn't like the cold.

I just ended up ditching the whole vacuum system and got the 4x4 Posi-loc cable actuated system.

 

[white7wolf]

4x4 posi... Lock... Cable... What??? Lol

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[white7wolf]

Oh ans thanks for the diagram it should help!

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[Canadian Expy]

The lever that goes in to the diff to actuate the center axle disconnect (# 24 - 25 above) will sometimes stick. It's a steel piece going in to an aluminium housing. Mine needed to be loosened up with a pair of channel locks and a can of WD40.

It could also be that the vacuum solenoid that activated the system could be on its way out and didn't like the cold.

I just ended up ditching the whole vacuum system and got the 4x4 Posi-loc cable actuated system.

Did you like this system? I've thought about getting it if mine fails..

 

[tonydiv]

4x4 Posi-Lok - 4WD Engagement Systems

It's the only way to be completely sure that your front axle disconnect is actually engaged.

 

[white7wolf]

Looks neat. You kinda have to give up the automatic part of it tho.
Anyways is there anyway to get a list of the part names that correspond to the diagram?

Thanks everyone

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[Canadian Expy]

4x4 Posi-Lok - 4WD Engagement Systems

It's the only way to be completely sure that your front axle disconnect is actually engaged.

Do have any old pics of it installed inside ?

 

[toms89]

Looks neat. You kinda have to give up the automatic part of it tho.
Anyways is there anyway to get a list of the part names that correspond to the diagram?

Thanks everyone

Sent from my galaxy s3

The transfer case is where the magic happens with A4wd. In A4wd the gem monitors for wheel slip and engages a clutch to activate 4wd "on demand". The sole purpose of the center axle disconnect was to reduce parasitic drag of the 4wd components while 2wd is selected. So you would just manually switch it when selecting between 2wd and the other 4wd selections using the 4x4 Posi-Lok. A4wd will still function perfectly well, going in and out of 4wd "on demand", as long as you leave the center axle "connected".

Hope this makes sense?!

1999 and later 1st generation expeditions actually did away with the center axle disconnect and 2wd selection.

As far as the exploded view of the axle I had saved that photo to my computer but do not remember where I found it. My 2000 expedition work shop manual does not have it because ford did away with the C.A.D. So sorry... no labels to correspond to the numbers.

 

[tonydiv]

All you see from inside the cab is the little knob peeking out from under the dash.
The whole thing takes an hour or two to install.

The cool thing about the system is that you can actually use 2lo (not sure how useful it is, but it's cool)

 

[white7wolf]

Ok i see now. Yes that makes sense.
Funny story.. Before all this i was showing 10.2 mpg. Now ive been driving around a4wd and my mileage now shows 10.5?! That's backwards lol

I guess the only way ill ultimately get anywhere is to crawl under there and open the sucker up and see if a part was stuck. The posi lock might not be a bad idea either.

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[white7wolf]

Okay so a thought occurred to me. Is it possible to just remove the whole center axle disconnect crap and have it operate in A4WD and 4-hi 4-low only, like on the 99+ expeditions? The small amount of gas mileage difference isn't much of a problem to me. Any ideas?

Thanks

 

[toms89]

Okay so a thought occurred to me. Is it possible to just remove the whole center axle disconnect crap and have it operate in A4WD and 4-hi 4-low only, like on the 99+ expeditions? The small amount of gas mileage difference isn't much of a problem to me. Any ideas?

Thanks

I would think you can just manually pull the lever so the center axle is connected and remove the vacuum control solenoid.

But tony would know better than me as I have not seen one up close.