03 f150 fx4 4x4
 

Hey fellas. I have a 2003 f150 fx4 with the electronic turn knob 4x4. It quit working last year and since winter coming I better get it fixed so hopefully someone can help. When I turn the knob it engages but on the ground it doesn't work. When I put it on jack stands and engage it it works. Can anyone help me out

The way you describe it can't be because the front actuator locks the front axles together.
.
Raising off the ground makes no difference.
Better check again to see what condition you really have.
The transfer case motor engages the front drive shaft internally.
The front actuator locks up the axles.
The control actions to accomplish all this are trouble areas you need to sort out.
Either is works or it does not. There is no in between.
Good luck.

why do you think "it doesnt work" when tires are on the ground ?

Well last year when I was looking into it I was hunting and couldn't get out of a tractor lane my rear wheels would spin but my fronts would not then when I put it on stands all 4 would spin. Made no sense to me so I figured I'd give it another crack

Its possible its not going all the way into 4 wheel. Mine was making a god aweful noise then I tried to use, but didn't quite make it into 4 wheel. Turned out the vacuum lines were coming loose because the hoses were cracking at the connection point. It could be as simple as replacing vacuum lines or even just making the connection better.

look at the vacuum cylinder on the front axle with the two vacuum lines on it. The rod strokes in and out with vacuum on either side. Maybe spray the rod and tap it in and out with a bump hammer or prybar to make sure it is free... might have stuck at one time and not engage.

another problem might be one mine had, the shift on the fly nob isnt as reliable and safe as it claims to be, my truck has it as well and i ended up having to replace all my four wheel drive stuff because with the shift on the fly when i put it in 4 wheel didnt fully engage and since it didnt lock in properly it shredded everything trying to run. had to replace the transfer case, actuator, and my entire rear end (but the rest of the rear end was for different reasons.) shift on the fly or not i would still say come to a stop and put your truck in nuetral or park before shifting to 4 wheel.

Thanks for all the help ill give it a try as soon as my truck gets back from body shop..I hit a deer last Monday morning

Alright fellas I finally had time to dig into this alittle further. The vacuum lines tested out fine so i hooked my vacuum tester to the vacuum actuator and it sucked the rod in and as I left it on there for a few minutes I noticed it very slowly lost pressure. It would have took awhile to drop all the way to 0 but it was falling slowly but surely so Im thinking that the Actuator is bad. What do you all think. Should I give it a try replacing it or look into it further.