Hi there. First time on the forum. I have a 2020 Xlt crew and I’m having a problem with my 4wd. The truck is making a humming noise coming from the front at around 25-30 mph. I switch it to 4wd and the noise goes away. Switch it back to 2wd and sound comes back. I have to switch back and forth from 2wd to 4wd a few times and eventually the sound finally stops completely in 2wd. Once I shut the car off and then start it back up the sound comes back and I have to do the process all over again. I’ve tested vacuum on all the lines,actuators,reservoir and the check valve. All good. Now the solenoid holds vacuum but when I start the truck I can’t feel vacuum out the hole going to the actuators. That hole should be pulling vacuum when cars on but is not. Until I drive and do the driving process (fiddle with the 4x4 switch), stop,leave the car running, check the solenoid then I can feel vacuum from the hole going to the actuator. So I’m stumped on the problem. I’m thinking it might be the switch/**** because I by passed the solenoid and the truck sounds and drives great. I just don’t have 4wd now. Has anyone had this problem? Or suggestions? Also the truck is leveled with oem raptor wheels and tires(315/70/17). When I put those in I had to replace the driver side cv axle. Maybe that could be the issue? Please help F150 gods!!!!

 

Ya its definitely the IWEs and almost everyone has had this problem! YOU ARE NOT ALONE!!!!

There could be a leak in the line somewhere, dirt, clog, the one way check valve could be blocked...and it could be the IWE itself.
Assuming its on warranty, let the dealer figure it out.

Did you replace the axle? or did you get the work done?
Wondering why the axle had to be replaced...and how were the IWEs handled when they were taken out?

 

Hi Stu. Thanks for responding to my thread. I replaced the axle myself. When I leveled the truck I torqued the nut too hard and snapped the threaded end of the axle. Pain in the *** to get out. I had to use a slide hammer but I believe everything went fine. All was goid for a few days.
Now if it was my iwe’s then why do they release when I by passed the solenoid? I’ve been driving like that for a day with no issue just that if I need 4wd I have to plug the two hoses back into the solenoid. I really don’t want to replace them if they’re fine. Ford won’t take them back if they’ve been installed.

 

Also wondering if my issue would be covered under warranty since I leveled the truck, bigger wheels and tires, and replaced a cv axle? Should I put it back to stock when I bring it in or at least put original tires back on?

 

Actually if I understand you correctly, you've diconnected the lines to the IWEs? So then they are both engaged.
Vacuum is required to keep the IWEs disengaged.
Therefore if you then switch to 4Hi the transfer case will engage and you will have 4wd...because your front axles are already engaged.

 

Nope. Connected the two hoses that go into the solenoid(check valve hose to the actuator hose). Trucks on I get vacuum. Shut truck off no vacuum.

 

I'm going to ask a few questions and explain how the system is designed to work just so we are all on the same page.

You tested and said everything passed.
I will assume you used a vacuum pump and gauge to read how much vacuum is pulled.
You would have tested:
Solenoid -making sure adequate vacuum is pulled and held stable
vacuum line at the IWE -making sure adequate vacuum is pulled through the line to the IWE and held stable
IWE -pulled vacuum with a vacuum pump and made sure it was not leaking off. This is testing the nipple on the physical IWE.

The IWE will disengage the hub with as little as 7Hg. Operating range is 15-20. The acceptable ''pass" is holding 15Hg for 2 minutes I think? I might have to look that up from a TSB.
By default, no vacuum is applied with engine off (obviously) and IWE is engaged to the hub (locked hub).
When vehicle is started, vacuum supply to the wheels is enabled, IWE retracts from the hub, unlocking the hub. Your 2020 model may take several seconds minimum to supply vacuum. It is temperature and time based. It will usually remain locked for a period of time, 2 minutes? while being driven at first startup.
When the TCCM tells the hubs to disengage, the solenoid is energized to allow vacuum supply to the wheels.
The check valve will hold the maximum achieved vacuum regardless of how low the vacuum is after that moment.

A leaking check valve allows vacuum to bleed off as vacuum from the motor is reduced.
A damaged IWE will bleed off and hub will want to return home, locking the hub. If you have reduced vacuum, the hub won't return home and will also struggle to stay disengaged. Normally a grinding type noise comes from the wheel area due to the IWE only partially disengaging leaving the hub partially locked/unlocked. Many times the sound is described as a ratchet type of sound, or rolling marbles/rocks, dragging a chain.

If the noise disappears when you remove vacuum to the IWE, it is most definitely one of them causing a problem. A simple solution we usually suggest is to disconnect the electrical connection from the solenoid (disables the unlocking of the hub). If noise is gone the entire time, then the hubs are remained locked and IWE should be considered bad by proving when the hub remains locked the noise is gone.


A visual test is to jack up the front of the vehicle and support it properly. Start the vehicle, leave it in 2wd and allow it time to unlock the hub. Spin the wheel and watch for the axle to rotate. If the axle is rotating, the hub is not unlocked. If it passes, shift to 4x4 and rotate the wheel again -the axle should rotate.
If the visual test and vacuum test at the IWE passes, it is less likely to be an IWE or vacuum problem. You would then need to turn attention to a bad bearing, perhaps.

I guess at this point, you have the parts in hand. You could disassemble the hub assembly/IWE to check for damage. If all is good and you wish to return the new parts, you can carefully reassemble. If you find one of the parts is damaged, you have the replacement on hand. It is a lot of money tied up to replace 2 parts that may not even be bad.

If you are under warranty it may be in your best interest to have it warranty checked.
Note: I do not know how they test now, such as if they still do as I described above or if there is a customer complaint they simply perform the latest TSB which is to cap the vacuum lines and send the customer home.

I hope that helps, and that it makes sense.

I don't think I missed anything, we do have a few resident experts that can make necessary corrections though.

 

Omg! Thanks so much for taking the time in responding to my thread. I’m going to take apart my truck today and go through and clean/check my iwe’s.
My only question is why is it that my truck is fine when I put direct vacuum to the iwe’s(no solenoid)? There’s no sound and wheels turn fine. Truck seems normal just can’t shift to 4wd on the fly.
Thanks again!

 

Yes, you can still shift to 4H on the fly, bypassing the solenoid only engages the IWEs, the TC will work as usual. When you replaced the halfshaft, did you make sure the teeth on the IWE were engaged before you torqued the spindle nut? 27-30ftlbs is required torque.
You will NOT have vacuum to the IWEs upon starting the engine. From 2017+, the IWEs stay engaged until the vehicle has been driven .5 mile. At that time, the solenoid is energized providing vacuum to the IWEs. This happens everytime you cycle the key.
Is this actually a hum, or sound like marbles being shaken in a can?
EDIT, my mistake, true, you won't have 4X4 with vacuum being fed to the IWEs continuously.

 

The description of Humm vs Marbles is importnat.

I suggest reconnecting the system as it is meant to be and at least check for freewheel. As well as listening to noises while you're at the wheel spinning it. It may be difficult to hear with the motor running but do your best.
If you are bored and want to disassemble everything you can but I would want to check what I can before taking it apart.

Consider this: The IWE and hub are actually fine, however you damage it during reinstallation once you've finished scratching your head in wonder after seeing the disassembled parts are not damaged.

Let us know what you find though -always good to have a follow up to IWE posts since they are so vast and somewhat random in what fixes the owners noises.