I think semi metallic pads are the best. they make a little noise cold but it goes away in minutes. I have used the ceramics and like the semi metalics more

 

Well gents, it wasn't the transfer case either. So let's recap:
Transfer case
Rear drive shaft assembly
Front hubs - twice
Left IWE and possibly the right (I can't keep track any more)
Rear diff cover pulled and gears inspected
Front diff fluid checked
4x4 vacuum lines and system
All 4 wheels removed and road tested with new ones from another truck - twice
Front drive shaft removed

Moving on to front diff disassembly and inspection. I appreciate the effort by the dealer, but this is absolutely nuts. I've owned this truck for a month and a half and it has spent more time at the dealer than in my garage. The service department has driven it more miles than I have! Does Ford comp owners for inconveniences and lost time with the vehicle at some point?
My other concern is the quality of workmanship on all the parts swapped out or taken apart. I might be getting back more headaches than I started with.

 

That depends on the person doing the work. For me, my friend who is a mechanic I wouldn’t have a worry in the world. The dealer I had work done at, I wouldn’t worry about to much either.

 

I debated on not getting this but here goes.... purchased a used 2016 Lariat 59k miles in May and now have 70k..... having same issues under 15mph here a terrible groan/rumble... turn 4A and goes away...in 2H put a 65 lb golden doodle in the back with a 50 or so pounds of luggage for Thanksgiving drove 1200 miles and never heard it in stop and go traffic.... empty truck to go grab something quick with an hour of coming home and instantly here the noise again... curious why weight would make a difference with this noise???

 

Never heard anyone say it comes and goes with weight changes. That being said, I can only think that the engine would be working harder (albeit it shouldn’t be that much harder with that little weight added) that the vacuum it is producing is less more frequently and your check valve has a slow leak where normal vacuum production over comes it but, can’t during those low production times.

Assuming it is related to the 4x4 system that would be my guess.

 

To add, replace the check valve. They will work intermittently and since yours comes and goes, that is probably the issue.

 

I told them the same, but they have not replaced it.

 

Sorry, that was intended for cbix50.

 

Any idea if a 73 lb goldendoodle is as effective? Ours blew by 65 lb about 3 years ago! Amazing dogs Btw.
your issue sounds more like the typical iwe vacuum related failure.

 

Yeah Goldendoodles are great dogs ! Thanks for info. Ordered some check valves we will see what happens.