Alright guys so I thought my 4wd worked turns out I was wrong. Looked under truck today and followed numerous lines and wires, found this!!!







I'm a noob to this stuff are these the vacuum lines? The blue, white and black lines are completely dry rotted. The red line seems fine but i have not gone in depth on it yet. These run to the front drive shaft so I'm hoping this is my problem.. Easy fix?? Thanks for any help

 

Yes they are vacuum lines. One engages the front diff, the other disengages. Any crack or hole will be a problem. The solenoid they are attached to on the firewall send vacuum through them to the vacuum motor on the front diff. That vacuum motor (which can be problem if clogged with a lot of dirt, snow etc) moves a fork that engages or disengages the front diff. Another problem can be the fork is broken. Somewhere around here there is a diagram of the system. Might try a search to find it.

 

Awesome thanks!! I should add that when put into 4wd low you do hear and feel that clunk from the t case. There's just nothing from the wheels. I called advance auto about the lines any chance you or someone know exactly what I need? Hose length/size etc... The rubber connectors on the lines are fine can I reuse them?

 

edit

 

Not sure of the size etc. Also unfortunately not sure which is the engage and which is the disengage solenoid. Also the solenoids themselves are known to cause problems.

 

Found these threads. Hope they help.

https://www.f150online.com/forums/v8...o-98-f150.html

https://www.f150online.com/forums/ot...um-system.html

https://www.f150online.com/forums/19...-engaging.html

Edit - After posting this, I see you found the one thread.