2016 expedition 3.73 4WD

in 2WD my half axles up front both turn with the wheels. It was my understanding that these half shafts only move with the wheels in 4WD. Had actuators replaced one year ago yesterday. I know from researching that it’s one of only a few things:

check valve(s)
solenoid
actuator seal
or the vacuum lines

couple questions, I see the check valve thts clear and blue up by solenoid drivers side firewall. Are there any others? Where are they? That check valve is good, only allows air one way when blowing in it.

Vacuum lines are behind attached to hub at the wheels. Best way to check vacuum in them, I do not have a hand pump

 

There's no good way unless you have a hand pump and a vacuum gauge. You could disconnect and blow into the end of the vac line that terminates at the wheel hub and listen for any hissing noise to see if you have leaks. But using your mouth, you won't get either enough pressure or vacuum to really be sure.

Best way would be to get a cheapo harbor freight hand pump and vacuum gauge, then disconnect at the check valve and use the hand pump to pull vacuum on the "downstream" side and see if you have any leaks. Then hook the vacuum gauge up to the system "upstream" of the check valve, start the vehicle and cycle the 4wd system. You should see vacuum in 2wd, no vacuum reading in 4A, 4x4 or 4x4 LO.

 

In the F150, the front axles lock in until the diff reaches temp. Don't know if the Expy is the same, but it wouldn't make sense to not.

 

Everything I’ve read is the front axles lock as soon as you turn the truck off, (no power to pull vacuum) and when started they are unlocked as the system pulls vacuum. First time I’ve ever heard of what you stated. Everything is vacuum related, no vacuum is 4WD and vacuum is 2WD

 

I thought mine was doing the same but i put it on a lift with the truck running so it would be functioning they way it would if i was driving. put it in 4wd check hub engagement then put back in two wheel drive checked it again and everything was working like normal.

 

Do you have 4A? If you do that's what goes on due to the clutch in the transfer case..
If not, bypass the solenoid by joining the two hose connections on the solenoid, and redo with your gopro or whatever you used.
Ya, it's a Raptor, but it'll explain to you what I'm talking about.
https://www.youtube.com/watch?fbclid...be&app=desktop

 

Read your Owners Manual. There is a section that refers to the front diff strategy being engaged for the first few miles. Perhaps try your test after a routine drive?

 

Ok I’ll give that a try

 

I do have 4a but never use it

 

It's pretty much the nature of the beast. Even when in 2H, some power is diverted to the front diff through the clutch.
Did you watch that video? The kid explains it very well.

Right about the 3 minute mark he talks about it.