I am still trying to diagnose front end grinding that has been going on for a couple years at low speeds... dealer has been no help. I am trying to test the vacuum to the IWE but have some question I am hoping someone can help with:

1) When I remove the boot from the vacuum hub, i don't get any hiss sound at all.
2) When I remove the line from IWE to solenoid, I don't get any vacuum sound at all with engine running and in 2WD mode.
3) The thick line coming off the check valve and going up and left to clip, in YouTube vides of newer F150 goes over and connects to vacuum supply... mine is capped and I see a cap on another line near engine (near oil cap). I have ONLY had this services at Ford Dealership since I bought it. They did replace the front diff about 3 years ago. Did they take that jumper off and leave it off for some reason? Why would they do that? (see in image). Is there any reason for doing that as a tech? Did they forget to put it back or did they do it on purpose to "fix" an issue? Is the 2016 model different? How would my 4wd be working without this? are my hubs ALWAYS engaged without this jumps and source of vacuum?
Am I testing something incorrectly? Hoping someone can tell me proper steps to ensure my IWE is getting proper vacuum in 2WD. I have a gauge, but all zero right now... what are the proper levels?
Thanks!

 

I have just read that part of front diff replacement does involve removing vacuum so the IWE remain engaged and do not get damaged. My dealer that did the front diff 3 years ago, also killed my new AGM battery while they has the car, and a year later I found they lost all my underbody panels, so I had them replace them... and now this vacuum line... now I am pissed, because I am concerned that having my IWE engaged 24x7 for 3 years has caused unnecessary wear and tear and loss of mileage, not to mention, MAYBE this front end griding I hear at stop sign speeds. Can anyone tell me what damage this may have caused?

I am contacting the dealer... even just to get it documented... who knows if they will or not. I could put a new hose on, but I want them to see it as they left it.

Thanks!

 

Per your photo,

For some reason, someone disconnected and capped the vacuum supply line. That's why you have no vacuum in any of the lines.
Your IWE's have been engaged all that time. I see you have a Lariat, so you have 4A. Ford came out with a TSB a few years ago oertaing to your truck. The TSB instructed the Tech to disconnect and plug the lines you have.
Did you say you were the original owner?

 

Looks like your front hubs are always engage, and always spinning the front differential, there is a line missing that supplies vacuum to the solenoid to disengage the front hubs, I bought my 2019 about 2 years ago and then after 2 months I found the one hub vacuum line off the front driver side vacuum hub, so I`m not sure how long my front end had been spinning in 2WD, since the last owner had it before I bought it, I had low growling noise and vibration when I would be slowing down, thought it was brake issue, but it was not, the front differential carrier bearing we`re destroyed, I crawled under the truck and I had slop in the pinion bearings too, so you might actually have failure in the front differential, below is my pics of front diff carrier bearings, I pulled it out and rebuilt the whole diff with new bearings and seals.

 

Wow, those are nasty!

 

Yes, original owner. Google says TSB for my year (2016) recommends to NOT cap the vacuum. later years 2020+ do cap under different TSB... if this is correct. I will have to find out if any service records show if they did this as past of tsb or accidently with the front diff replacement. It was only 3 year ago... I should not be having another front diff failure!!!! If they really replaced it.
Is this right, or is there some other TSB that has them capping that vacuum line on a 2016 F150?
Either way, if I put it back in to engage the IWE in 2WD mode, and my griding goes away, does it point to the diff?

For 2013-2018 F-150s (TSB 20-2252): (google may be wrong on #... looks like it may be 19-2252)
This TSB focuses on a potential loss of vacuum to the IWE actuators or wear of the IWE components, which can cause a grinding noise in 2WD mode.

1. Do not disconnect the vacuum. This TSB does not recommend disconnecting the vacuum.
2. Follow the provided Service Procedure: The fix involves reprogramming the Transfer Case Control Module (TCCM).
3. Replace faulty components: Any worn vacuum components or IWEs should be replaced as part of the repair process.

 

Wow. I hope it is not my diff... but the sound I hear has been happening for 3 years since they replaced the diff with a brand new one under warranty. It has gotten slightly worse over the 3 years. I can't believe that they would cap the vacuum line to "solve" a grinding issue... causing more wear and tear on my vehicle... I am not a mechanic... but, am I correct in that capping that line and thereby keeping IWE engaged always, will always have the axles spinning all the way to the differential... and possibly degrade the diff faster if there is an issue?

 

After more research, there are 6 TSBs over the last 5 years on this... each one replaces the last. The early ones were misleading and did not differentiate between ESOF and TOD... and the later ones differentiate between ESOF (no 4A) and TOD (4A). For ESOF, they recommend fixing the vacuum issue... for TOD/4A they recommend removing that line, effectively locking the IWE forever. So, that is probably what was done on my vehicle. WHY, would Ford not actually fix the issue instead of just disabling the IWE????? Does anyone know what the underlying problem is they were covering up? IWE issues? Hose issues? Solenoid issues?

But now, my front end grinding that is getting worse... if I put the vac line back in, then my IWE should work again (I will verify proper vacuum and that it holds). Would that help me at all in trying to diagnose this grinding noise at least? Am I correct in that with the vac line attached, and in 2WD mode, my wheels should be spinning freely and not attached to the CV joint, axel or front differential, correct? If the noise goes away, can I conclude it is CV, axel or differential issue? If the noise persists, is it safe to say it is an issue at the wheel... IWE, bearing, etc?

Thank you!

 

Mine is Lariat and has the 4A(TOD), how I found my issue was check the front differential flange and I was able to move it a little like, .015"-.020" ....should be no slop (I`m not talking about backlash in the gears, but my Backlash spec was way out of spec because of the bad bearings and loose pinion bearings) , since the the pinion bearings have a preload on them, you will need to get Vacuum to you hubs and verify they are disconnecting the front axles at the wheel hubs, once that`s checked and they are working, then you have to remove the front driveshaft...... if you have the 4A and if the noise is gone then, you front diff needs fixed, that`s how I found my problem, what I have found out with my research the 4A(TOD) transfer case still spins the front driveshaft in 2H, the clearance between the electric clutch in the TransferCase of the (TOD) is small and with the fluid in there it still creates drag and still cause the front driveshaft to turn, they say you would be able to grab it with you hand and stop it from spinning, so in theory going down the road the front shaft will still be spinning, but not as fast as the rear driveshaft, so hopefully this helps you track down you issue. mine started doing this about 4-5 months ago, and I tired everything to find the issue and thought it was front brake pads and rotors, and wheel bearings, but from the pics above you can see that wasn`t the case.

 

Thanks! Was your noise constant as you were slowing down, or was it intermittent? When you fixed the lines and put yours in 2WD mode, did you still have the noise? Or was it only present when the IWE were connecting the axle and the wheel?