I have a 2020 3.5L Ecoboost with approximately 83k miles. I've noticed a moaning/groaning noise as the RPMs drop while slowing down. Not a grinding or metalic sound. This is in normal day to day driving in 2H with and without the breaks. Outside temperature doesn't seem to change it. Stops when the truck stops and doesn't happen every time. I've heard it can be the front hub vacuum system, but wanted to know if anyone else has experienced this.

 

Possibly an IWE, but I'd also check u joints, pinion bearing, and parking brake. IWE is usually when turning.

 

Mine was the hubs and IWEs. Sounded like I had mud tires on it before I changed them.

 

Come to think of it, I had a similar noise on my 2010 years ago. It ended up being (according to the dealer) the aftermarket leveling kit. They said it created some sort of harmonic effect. Worth checking if you have leveled.
Also, 82>101...

 

My guess the hubs. If you go into a parking lot does it change sound turning left or right?

 

Also when it does it, switch it to 4h(as long as you're driving straight) and see if it goes away. Then you'll know that it's IWE's

 

^^^ This ^^^

 

IWE is the right call to investigate first. A quick test: next time it happens, try briefly engaging 4WD Hi while moving slowly in a parking lot, then switch back to 2H. If the noise changes or stops, the IWE is almost certainly your culprit. On the 3.5 Ecoboost these hubs are vacuum-actuated, so also check the vacuum line that runs to each hub - if a line is cracked or disconnected, the hub can sit partially engaged and create exactly the kind of intermittent droning/moaning you're describing.

At 83k miles the IWE seals are commonly worn on these trucks. Motorcraft replacement units are around $80-90 each and it is a pretty straightforward swap if you're comfortable with front axle work.

 

Also check the auxiliary vacuum pump. I know of a couple of cases where it was the vacuum pump failing that caused the IWE headaches.