Had the 17 Lariat at the dealership for the 50k mile service recently... got it back and over the following week or so, started hearing a deep sounding knock during idle. It matches the RPMs and goes away with any increase on the tach... I've tried to listen where it's coming from but frighteningly, it seems like it's from deep inside. Oil level shows full on the stick and this knock occurs whether fresh start or fully warmed up and driven.
Naturally it's headed in for a checkup but I figured I'd bounce it off you guys for ideas...

 

Is it the 3.5L? I have a 2018 and it developed a knock when it was warm at idle. They had to replace the cam phasers and so far quite as can be. My knock was coming from the passenger side.

 

Nope, 5.0... I'm nervous as hell

 

Why are you nervous? Per your first post, you are well within your 5y/60k powertrain warranty.

 

If it's in sync with rpm and located "deep" in the engine, it could be a rod bearing.

 

The one thing that’s interesting about what you’re describing is it’s there all the time and not just when the engine is hot, i’ve heard a deep hollow knock, I caught more of a thumping almost like someone tapping on the bottom of a 5 gallon plastic empty bucket, In about a half dozen F150s now doesn’t seem to matter what engine.
my old 2013 had it and I took it in time and time again to have it looked at even had a couple long blocks replaced and it always came back or never left.

I now have a 2019 3.5 and it has the same damn knock from the day I pulled it off the dealership lot, I didn’t notice it until two days later though. I took the truck in at 12,000 miles to have it looked at and Another sound and the shop foreman couldn’t even hear the thumping I was talking about but they ended up replacing my phasers and turbos for the other sound which took care of that. Wow my truck was at the dealership they gave me a 2019 rental and sure enough had the same exact thumping sound.

Take a listen to the video attached, it’s not the easiest to hear but it’s definitely noticeable. Mine only happens in drive or reverse and only after the truck is up to temp and from about 500 to 1200 RPM’s

 

Warranty would certainly cover any issues, so that's good but I just hate to think that my beautiful truck may have an engine issue.
That vid does have that knock... I'll have to get a clip and see if it compares; it's hard to hear from a phone recording.

 

You take your truck in yet?