IWE vs. Check Valve
 

I complained twice to the dealer about grinding in the front. First they said nothing wrong and next time they confirmed grinding and replaced a "check valve" Now the grinding is back, not always, just once in a while. Are these two separate issues?

I ask because it seems like IWE issues arise during acceleration, at least according to some of the reading I've done. My grinding occurs only when driving at a constant speed and immediately stops when I tap the brakes and resume speed (and then comes back some times).

I have 33,000 on the truck and want to make sure I get anything done under warranty if I can. I'm just tired of going to the dealer all the time. My truck has never stranded me, but 3 trips for front end noise, 2 trips for back up camera, two trips for peeling paint on the running boards (as well as regular maintenance) is quite a lot in less than two years.

Replacing the check valve or the solenoid accomplish basically the same thing.
It's not unreasonable to say the check valve is/was bad, however they are replaced more often than not unnecessarily. Replacing a solenoid is next to zero... some have but 98% of they say it was not the solution. Okay, not really 98% but 2 people here (that I can think of) have claimed the solenoid is what fixed the rattling noise of the IWE.

If you were to take it back, I really doubt they will replace the solenoid and say "let us know if that fixes the problem" because it's highly unlikely to have failed. It has to fail internally and not seal off when open which would allow vacuum leak.

First in order is the solenoid. It is closed so no vacuum is pulled through the solenoid. When shifted to 4x4, solenoid opens so vacuum is drawn at the IWE (unlocking the hubs).
Because vacuum rate is varied, a check valve is next in line after the solenoid. A check valve allows air (in the case) to pass only in one direction. The check valve prevents vacuum loss as manifold pressure is reduced. If the check valve leaks, vacuum is reduced allowing the hub to attempt to lock, but not fully as there is still some vacuum holding it back.
So if the solenoid fails, the amount of vacuum supplied may not be adequate. If there is 'never' enough vacuum for the hub to fully unlock, the check valve then wouldn't matter as not enough vacuum has ever been met for the check valve to even be effective.

Discussing instant noise/silence with a brake tap would lead me to a brake inspection. Even tapping the brakes lightly should not affect vacuum enough to say an IWE isn't working properly. If the check valve is working, vacuum changed based on brake booster vacuum will not affect the IWE system. Could potentially lead you to a solenoid, if the solenoid is leaking but again, highly unlikely.

I don't think your problem is either one.

There is a third option some of us have experienced that you might be mistaking for IWE failure. There is a pinion bearing in the front diff that begins to walk itself out 1mm or 2 mm over time. Ford came up with a shim kit for it. I'm not sure what the TSB number is, but I thought there is one. It may momentarily reseat itself and stop making noise such as when braking as you described. It sounds and behaves identical to IWE failure in every way (I've had IWE's fail on my other F150's). This pinion bearing issue is not uncommon. Best to get it resolved while under warranty. Part numbers attached below for reference.

Here is my old service records for it from my 2017 F150.

The service shop I went to (City Ford in Edmonton) is usually pretty good. They thought it was the IWE's the first and second time I had it in. There's more paper work than what's shown. These are just parts for reference.

It was actually my service advisor who correctly identified the problem :thumbup: He had the exact same thing happen on his 13 Gen F150 a month or two before mine failed, so he was able to make the correct diagnosis without even looking at it LOL. By that time it was my third or forth visit for it.

1. Suspected issue resulting in unnecessary IWE and vacuum line components replacement.

https://cimg4.ibsrv.net/gimg/www.f15...45f2fccbbe.jpg

2. Actual problem, Pinion Bearing Shim:

https://cimg0.ibsrv.net/gimg/www.f15...54aeea8222.jpg

I went through somewhat of the same situation. It turned out to be a small chunk of gravel that was trapped behind the brake caliper shield. Once I got that out of there, no more noise.