Hi all, first time here to the forums.

I have a 99 XLT 3.0L 4x4 and I am pretty certain that my 4x4 is not working. I have searched the net for various help on diagnosis but still I can't figure out the problem.

I'll start from the top here... When I switch the truck to 4x4 hi via the switch on the dash.
Everything seems to work perfectly.. the light on the dash switches to 4x4 and I can hear the actuator clicking to the next position underneath the truck. I have even removed it completely and tested to make sure its working and it definately is. However the 4x4 still does not seem to work. I have tried mashing the gas in the snow to see if I could see spin marks but the truck still moves with just two wheels so that isn't helpful. I also tried putting it in 4x4 and making sharp turns.. as of yet I haven't had it "hop" on me. Which makes me believe is not working.. Also last winter I got stuck in my driveway with only a tiny notebook size stack of snow on the ground while my truck bed was full of wood.
So this also makes me believe that the 4x4 is in fact not working..

I suppose my question is how do I go about fixing it now...? I haven't ever done 4x4 repair, though I am not exactly a stranger to mechanics. I'd like to zero in on the most probably cause of the issue and try fixing that.. I don't have alot of money and this is my only vehicle.. so if I have to take something apart (which i'm sure i will) i need to be able to wax it all out in a single day.

Thanx for any help you guys can offer me

 

Check all the visible linkages up front. Make sure the driveshaft is spinning when the 4x4 is engaged and if it is, the problem may be in the front diff.

I'm not a 4x4 owner but thats all I can think of. Someone will come along who knows things.

 

Thanks for the suggestion.. would the truck need to be moving for the driveshaft to be spinning?
atm i got no jack/lift to pick it up off the ground.

 

check the vacuum lines running to your front hubs. Also a sure fire check for the motor is turn it to low range. If it goes into low its not the t case or the shift motor.

 

There is a Vacuum switch of sorts on top of the passenger side frame rail.
You should disconnect the main line and connect it to one of the wheels directly to see if that locks it in.

It is most likely a vacuum issue.

 

On pvh trucks you need to use a hand vacuum pump and check leak down of the knuckles. Before you digging anywhere else. Typically the seals leak air where the half shaft passes into the wheel bearing.

Honestly buy the manual hub conversion by AVM, Tellico or Milemarker. They are all made by AVM so find the best price.

 

I had it in 4-low during my driveway stickery and it didn't change anything.. it did switch over clicking and light etc..but no change in mobility. It was truly sad.. a 4x4 truck stuck in virtualy no snow with big tires, good tread and yet my gf's volkswagon(sp) drives through it and more. I'll have to go get the repair manual for this and take a look at the vaccum hoses as suggested. Thanx for help guys.. i'll post back when I have an update.

 

I just wanted to share as this post/forum helped me w/ my 4x4 issues. Got a used truck and prev owner said needed xfer case. But, I suspected electrical as nothing happened when engaging 4x4. Got a 4x4CM from a salvage yard, my model was AC, the used one was AB from a Ford Explorer. Didn't work w/ cold swap, but took it to Ford and during there diagnosis/clearing codes, it started working. So perhaps if your 4x4CM is fried, and you get a new one that doesn't work, try getting ford to clear the codes and see if they can get it to work. Maybe it would have worked cold swapped w/ a new one, or exact same model from a Ranger, who knows. But my 4x4 is working for 100$ used part and ~2hrs labour at Ford! Considering the price I paid for vehicle was well lower due to no 4x4, I'm quite happy now!