I have an 06 XLT, having issues with my 4wd, 4hi and 4lo dash lights come on and both make engagement clicks and clunks but it isn't actually going into 4wd. Sometimes (rarely) it will go into 4wd and work. Both actuators have been replaced a few months ago and the vacuum lines are attached and look in good shape as far as I can see. It also has old style solenoid on it (from factory)

Any suggestions?

Note: seems to engage and work properly when first started or battery reset

 

Bump ?

 

Since it has the old IWE Solenoid ...I would replace it first and then if that don’t solve your engagement problem.. rent a vacuum pump to troubleshoot.

 

https://www.f150forum.com/f4/4x4-tro...g-guide-39789/