My dad has the same truck as me, ( 06 F150). The 4wd control is manual shift from the floor. The lever is moving free and the indicator lights are working properly. It will shift into 4x4 high and low properly. The transfer case is working properly. I can feel it go into low range, obvious difference in gear ratio. Also I checked to make sure the front driveshaft was locking up when i shifted into 4x4. The problem we are having is the front wheels won't lock up (scuff). Since this is not electronic like most are, i'm not sure what to look for. I was told there is a vacuum controlled collar or device on the right side of the diff housing. That could be bad or dirty? Vacuum line problem? Any help or ideas? Thanks in advance.

 

The hubs are controlled by a vacuum. I would start by checking them. With no vacuum the are locked and with vacuum applied they are unlocked. When you put the truck into 4x4 a solenoid (Located on the firewall right behind the battery) removes the vacuum and the hubs lock up.

To check the hubs do this....

Jack the front of the truck up. With truck running (leave in park) in 2wd turn the front wheels by hand. Watch the CV axle to see if it is spinning. It should not be spinning right now when you manually spin the wheels.

Now. Put the truck in 4x4. Spin the wheel by hand again, now the cv axle should be spinning.

If the CV axles are not turning while in 4x4, my guess is your problem is in the solenoid. It probably isn't working and releasing the vaccuum. It is pretty common for them to fail and they are pretty cheap and easy to replace. One final check to do is to pull the vacuum line from the back side of the hub. It is a rubber hose with double lines, one big and one small. Do the wheel spin test again. The CV axle should now spin, regardless of if truck is in 2wd drive or 4x4, because there is nor vacuum applied to the hub and no vacuum=locked hub.

So do these tests and this should help you at least narrow things down a bit. Good luck!

 

Thank you, I will give it a try this weekend.

 

Yesterday I tried a different solenoid from my truck. It is getting vacuum and I think it is working ok. 4wd still not working. The left hub is clicking and to the best of my knowledge is not locking in. Do I have to replace the whole hub assembly? Do I need any special puller to get the hub off? Thanks in advance.

 

https://www.f150online.com/forums/ar...then-some.html

 

Found out tonight it is the 4wd actuator on the driver side. Ordered one, hopefully I can get it installed this weekend.

 

Thanks for the link. Helps me understand everything I've been starring at for a week.

 

i have seen moisture get inside those vaccum actuators and then freeze if its cold or even rust inside enough that they start acting up.

not real bad typically to change them but it can be a pain if things are rusty.

also there is a seal between the actuator and the housing and if it starts to rust it can cause vacuum leak problems.
thay all result in 4x4 not working when you need it to.

 

I replaced the 4wd actuator on both sides. The driver side fell apart when i took it off. and the pass. side was blown out and would hardly move. That fixed the problem, works great now. Thanks for all your help.