So in reading about the 4x4 system for our 2004 Navigator, I'd seen it indicated that in the 2H setting there was a vacuum disconnect for the front axle/hubs, so that the front wheels would "free wheel" and not turn the differential/axles/driveshaft.

Just was out checking for wheel play (Firestone said I need tie rod ends), and noticed when turning a front wheel that the driveshaft does in fact turn with the front wheel.

Does the vacuum operation work such that it only "unlocks" when it's running?

Is something amiss with my system?

Or is my information just plain wrong on the principle of operation?

 

Nobody knows?

 

When checking for the hubs being locked/unlocked, the engine has to be running at idle because vacuum is required to lock/unlock the front hubs.

 

Here are the pinpoint tests. Go to page 29 "PINPOINT TEST E: THE FRONT AXLE DOES NOT ENGAGE CORRECTLY".

 

thank you!