What are the most common reasons?

[Eddie Rod]

What are the most common reasons the 4x4 stops working in the second gen expeditions?
I have an 03 Eddie Bauer and 4x4 seems to not work.
I have changed out drive shaft u joints, front wheel hubs, tccm and still no luck. I can hear a "thump" when put into 4lo or 4hi which I assume to be the front wheel hubs engaging. A few days ago while in some sand I placed it into 4x4 and heard a "chain dragging" sound under the truck and had no spin in the front wheels. Any help any advice is greatly appreciated!!

 

[riphip]

Vacuum related problems. Check all your hoses, etc or get a smoke 'machine'

 

[Eddie Rod]

Vacuum related problems. Check all your hoses, etc or get a smoke 'machine'

Thank you! That is actually my next move. I have some check engine codes related to a vaccume leak as well. Hoping that when they fix that they will find the root of my 4x4 not working.

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[riphip]

I would check those going underneath at the accutator(s) & the hubs first

 

[Eddie Rod]

I would check those going underneath at the accutator(s) & the hubs first

That's a great tip, I will make sure to have those looked at first.

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[lbv150]

Chain dragging noise? That would be the transfer case and the chain inside let go....Time for a new transfer case.