2015 Ecoboost - Humming from Front Driver Side Wheel in 4A

[Aaron407]

I wouldn't be as concerned if it had always done this, but it was fine for the previous 155,000 miles and just started making the louder noise.

 

[Aaron407]

Latest update: I just tested both front IWEs under vacuum. They both held 16" with no issues, including when rotating the wheels.

I also tested vacuum level from the system at each IWE, which came in at 26". There was no variation when cranking the wheel either.

Since everything seems to be locking and unlocking as expected, but it will still go without a hum for a short distance after going full left lock, I can't help but wonder if it's the wheel bearing getting shifted a bit and re-seating to the noisy position after that distance (which is weirdly consistent, by the way). There was no discernible play in the bearing, though.

One thing I hadn't mentioned is that this vehicle spends a large amount of time on the gravel. I didn't see anything, but maybe there's a stone lodged somewhere? Kind of grasping at straws...

 

[Aaron407]

New updates in my hopes of figuring this out:

I replaced the hub/bearing and IWE. Everything's back together and functioning, but the sound is still there. I also noticed that abruptly pulling off the throttle when at highway speed will usually see the sound briefly go away completely. I'm making an appointment to take it into a shop, but the working theory now is a bad pinion bearing in the front differential. I guess we'll see. I'd be open to any other thoughts as well!

 

[tacoduck]

Just curious, why are you running in 4a at highway speeds? I was told growing up to never run 4wd above 45-55 mph.

 

[Aaron407]

4A is fine to use basically all the time since it just adds spinning weight of the axles with the IWEs locked but nothing is actually being powered unless there's a loss of traction since the clutch isn't normally being applied in the transfer case.

Per the manual regarding 4A: "This mode is appropriate for all on-road driving conditions, such as dry road surfaces, wet pavement, snow, or gravel."

We live on a gravel road up in Saskatchewan and like the extra assurance versus just 2WD mode. We don't run in 4x4 mode unless we're really stuck, though, as that would be continuously applying the clutch in the transfer case and would be brutal on the driveline on dry ground.

 

[Aaron407]

Final follow-up: we took it into a shop and they found the CV-type joint on the front driveshaft was broken. They replaced the driveshaft and the noise is gone.

 

[Machete]

Service your transfer case. Also, I don't recommend only doing one axle. Its like doing ball joints or shocks on one side.