In many cases, that's the first thing I recommend. Doesn't fix them all, but it's a cheap easy thing to do. That little item has caused damaged IWEs if left to go too long.

 

I just replaced my check valve with the new assembly that has the blue valve in my 2017 with 35k. My grinding/vibration is less but still noticeable in certain driving situations usually under 20 mph and when I am coming to a stop. I feel it in the brake peddle. I can feel the rotation of the wheel. It definitely goes away in 4A. Does it hurt to tow in 4A? I scheduled an appointment with my dealer to check on it.

 

Ford says 4A can be used on any road conditions, but I don't recall reading anything about towing. What you could do without affecting the TC at all, is just pull the power at the solenoid.
In fact, Ford has a new TSB that does away with ALL vacuum going to the IWEs.
https://www.fordservicecontent.com/Ford_Content/vdirsnet/TSB/EU - MC-10181917-0001.pdf

 

Wonder what are the downsides to this TSB? Worse mpg?

 

That's possible, I couldn't say how much. It will add wear and tear to the front diff, how much? Can't say there either.
Where I see a real problem, you get some guy who knows how the system works, 4X4 that is, and realizes that Ford negated an option he paid for, and now doesn't work as designed. Now this guy is a law suit looking for a place to happen. Just my opinion, it doesn't affect my truck.
Appears Ford gave up on some with Torque on Demand. They may be able to prove in court it's a better fix, than doing the right fix.
No doubt they've got their butts covered somehow.

 

It would be interesting if someone would mount a direct reading vacuum gauge on the console somehow, tie it into a vacuum line which goes directly to the actuators and monitor the level of vacuum. Find out first what the minimum amount of vacuum is required to fully retract the actuator out of Its 4WD position. The IWE system reservoir will store the highest vacuum produced by the manifold via check valve and that's what you should read on the gauge. Any small vacuum leak should show itself when the engine is off. I may even show itself when cruising down the road due to lower and fluctuating manifold vacuum.

Second thing is the actuators. If vacuum to the actuators remains above a minimum requirement when you have a grinding noise, one of the actuators is at fault, sticking rusted, corroded or whatever. To determine which is the problem should be easy for a Ford Tech.

Just as a note: An actuator is sprung loaded meaning, it defaults to its 4WD position. Vacuum to the actuator assembly pulls it out of 4WD into 2WD against its spring pressure. The vacuum must be present full time to remain in 2WD. When vacuum weakens for whatever reason, the actuator moves slowly toward meshing with the 4WD hub gear and you get the grinding noise. There must be some vacuum still present when the noise occurs or it would just completely go into and remain in 4WD. The question is how much. Well, if could monitor the vacuum going to the actuators, you'd have the answer.

 

What's the fix for a XLT, STX/XL that doesn't have 4Auto, just part time 4WD. I had my 2012 fixed right away with new vacuum hoses when I heard the grinding. No issues after the hose replacement.

Seems like a lot of vehicles run with the hubs locked and just the transaxle/differential activates the 4WD/AWD. At least the super duty trucks use a manual locking hub where you can leave it locked in all winter and unlock it after winter, and use as needed. Unless they changed their hub operation in 2017 with the new truck design.

 

I think it's 8hg for the IWE's to disengage IIRC from the troubleshooting flow from Ford.

 

Mostly correct, but when the IWEs start engaging[partially], and cause the grinding, the system is NOT going into 4X4. You have to shift the TC.
Did I read your post correctly?

 

The fix is the same for ESOF and TOD.