Hey Ford Techs....2016 Expedition issue

[Jim Oaks]

So I performed a test today that may sound stupid....

With the truck running and in 2WD, the front axleshafts shouldn't spin right? Engine vacuum should disengage them.

I took some blue painters tape, wrapped it around each axle, and attached the other end to a swaybar link. I backed down the driveway a little, pulled back up, and the tape was intact.

I drove around the block getting up to 25 MPH and pulled back in to the driveway to check the tape. The tape on both sides had broke and wrapped around the axleshaft, which tells me the front axleshafts are turning in 2WD. I don't get any noise from the hubs trying to engage on either side, I can just feel that the wheels are connected to the axle, and get a humming sound at higher speeds from the shafts turning.

So both hubs are fully engaging when driving down the road. Wouldn't that be more of a problem with the vacuum system itself? I would think if one IWE was bad I would just get that shaft spinning. Maybe if there was a leak in one, it would cause a reduction in vacuum to the other side, and cause it to grind because it's not fully engaging, but both of mine are engaged.

My axle code is 15, which should be a 3.31 ratio with an open differential, so I wouldn't think that one front axle would be causing the other to spin.

SO......

Neither front axle spins at low speed.

Both fully engage driving down the street.

No grinding from partial engagement.

Does this spark any suggestions?

 

[Jim Oaks]

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I performed more tests today.

I disconnected the vacuum lines from the solenoid, and connected them together so that the hubs would have vacuum. When I pulled the hose off, I heard a lot of air escaping.

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With the lines connected so that there's always vacuum, I did the tape test again on the axle shafts. Again, the shafts were still turning, and broke the tape.

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With the engine off, I jacked up the truck and spun the wheels. They spun freely from the axle shaft because I still had the vacuum hose stuck together. This tells me that the 4WD hubs are working, and that the lines are holding vacuum.

I then reconnected the solenoid, and checked the hubs again.

Engine off - hubs engage the shafts
Engine running - hubs disengage the shafts
Engine running and 4WD set to 4HI - hubs are engaged with the shafts.

WTF? Why are the shafts engaging with the hubs when I'm driving?

 

[Jim Oaks]

Looking at this from a different angle, is there a way that the transfer case can be engaging as I drive, and spinning the front axle shafts? It's in 2WD, but it has the 4A, 4H and 4L settings.

 

[snoranger]

Looking at this from a different angle, is there a way that the transfer case can be engaging as I drive, and spinning the front axle shafts? It's in 2WD, but it has the 4A, 4H and 4L settings.

Pull the front driveshaft and do the tape test again.

 

[Jim Oaks]

Ok, let's say I do that.

If the axleshafts still turn, then the hubs are obviously engaging, but I don't see how. The lines and hubs held vacuum after the truck was shut of with the solenoid bypassed.

If the axleshafts don't turn, then the t-case is engaging (remember it didn't do it backing up and down the driveway), but what would cause that?

 

[adsm08]

Ok, let's say I do that.

If the axleshafts still turn, then the hubs are obviously engaging, but I don't see how. The lines and hubs held vacuum after the truck was shut of with the solenoid bypassed.

If the axleshafts don't turn, then the t-case is engaging (remember it didn't do it backing up and down the driveway), but what would cause that?

Wiring or control module issues.

I once saw one where the power mirrors would move themselves at random, that was caused by a bad GEM.

 

[Jim Oaks]

It sounds like this transfer case leaks power to the front driveshaft.

I've wondered if my left front axle is worn out because of the vibration at higher speed. I have around 73,000 miles. I wouldn't think that the shaft would go bad yet. Is there anyway to inspect the shaft without having to tear the front apart?