Ok, I have a doozy of one. I'm suspecting the IWE's are blown, but I'm going to go through this anyway. I'm not getting the grind that the IWE tsb covers. Other posts on this haven't associated this with the 4x4 system which I believe it's tied to since that is what has directly affected the sound.

2019 F150 platinum 4wd, 7,300 miles, shift on the fly setup with Bilstein 2.1 level. Ford refuses to do any diagnostics and says they can't hear it. They said drive it until it breaks, then we'll fix it, but it's too annoying to keep driving like this.

I have a thumping sound coming up from the driver side floorboard. I can feel it in the floor board and the gas pedal. From the passenger seat, you can faintly hear/feel it, but it's still there. I've done lots of testing in different setups, so I've listed below the conditions and the sound/feeling. I've only done it between 2wd and 4A because it's essentially the same as 4hi because the hubs lock in. All occurs under light throttle enough to maintain speed or barely increase speed generally around 30-35 mph the best, but can still be heard/felt at other speeds. I've replaced and added two check valves in series and I've replaced the solenoid.

Factory setup, all hoses and connections checked
2wd-thumping all the time
4A-intermittant thumping
When shifting from 2-4a, you can hear the thumping get louder and then disappear once 4a is engaged then it'll be intermittent.

Unplug electrical to solenoid, so hubs lock in, all vacuum lines still connected
2wd-thumping still present, but better. Thumping seems to have shifted to appear more when accelerating rather than light throttle
4A-only occasional thumping
As expected, no thumping on the 2-4a shift on the fly since the hubs are already engaged.

Unplug and cap all vacuum lines from solenoid so hubs stay locked in
2wd-no thumping, butter smooth
4A-intermittant thumping
As expected, no thumping on the 2-4a shift of the fly since the hubs are already engaged.

Unless I'm wrong, I don't think it's a transfer case issue because that would be more apparent in the shift on the fly process after I had already plugged the lines. My inclination is to get the RCV IWE eliminator kit, but I'm worried with the noise coming back up in 4A with everything plugged, it might be something else. I'm beginning to scratch my head. Any other tests I should do to check them before removal and inspection?

 

Bueller, Bueller, Bueller....

 

My truck is a 2019 with 3,500 miles and I've started noticing a slight thumping sound from the same area. But I am only noticing mine when I am going slow and applying the
brakes lightly. Going above 25-30mph I don't notice anything.

 

so did you ever find the issue? i'm having the exact same thing on my 12 screw eb. it's happened multiple times and each time the IWE hubs were shot. this time they weren't really bad but one was. i got pissed off and took the ring gear out until i get some Deletes in the mail. i really want this thumping to stop. Strangely even with the IWE ring gears out (the hubs and cv's can't spline together) i still get intermittent thumping. of course it doesn't matter if i'm in 4a or 2wd because my hubs can't lock. any thoughts. I will take it in to have the diff fluid and transfer case fluid checked. what did you find though.

 

I've found nothing. I have not installed the delete kit yet because I'm leaving it factory until the warranty is up. I've just left the lines plugged up and it seems to help the most.

 

I subscribed to the thread so I can watch developments. I have the same issue on the passenger side. Mine is intermittent, and mostly occurs from 50-65 mph on uphill inclines when stepping on the gas to maintain speed. 4X4 functions perfectly, and makes no difference in the thumping whether in 2X, auto or hi range. It doesn't thump if you are over 70 mph. My driver side IWE went bad and was replaced under warranty. It exhibited the typical symptoms that immediately went away as soon as auto or hi range was engaged.

 

I would say your passenger side iwe is bad. Possibly a vacuum leaks at the hub end in the diaphragm, that is exacerbated when you hit the gas. Hitting the gas changes the vacuum in the manifold.
someone floated the idea of a broken tire belt.?
Im thinking that’s an issue in the diff would not be so rhythmic. A CV axle possibly? But I think I would notice something while turning like most CV issues.

 

I ordered a Dorman delete because it has the post where vacuum lines attach.
my other IWE’s have gone bad in strange ways. We don’t have much humidity so it’s usually not water buildup. But the diaphragms have separated. The black gasket has cracked and the gasket and spring got bound up in the ring gear. All kinds of weird. I’ve gone through 3 sets. All have been warranty replacements of each other which is nice. But the shredding and self destruction caused me to replace my wheel bearings.
there is also now scaring on the cv axle shafts that goes into the wheel bearing due to debris.

 

deletes have eliminated 90% of the problem. it faintly comes and goes. i feel like something in the front end that spins could be slightly out of balance. i'm thinking the CV's could be loose enough in the axle that hitting a bump causes them to wobble a little bit.

 

Ttukayaker88, did you ever find the solution?