[OilDripper]

OK, so I continue to play whack-a-mole with my 2011 F25 3.5. The latest thing that has popped is a whining/humming/resonance that I think is coming from the front. The odd thing about it is that: (i) it ONLY occurs when decelerating; and (ii) if you put the transmission in neutral while decelerating the noise goes away.

I have replaced front hubs and rear hubs in the last 12 months and changed diff and transfer case fluids in the same time period. No metal of note in those fluids.

My Blackstone engine oil anlalyses continue to come back clean.

The car has 188,500 miles on it.

Can't really think what it would be as I can't envision why the noise would stop when I put it in neutral. I would think that would imply the noise is coming from the engine as the revs drop to 800 or so when it is in neutral - the sound decreases with speed (and engine RPM). But if it WAS from the engine, why wouldn't I hear it when under load (unless the engine sound is masking it, which I don't think it is as the sound starts a second or two after you lift off the gas).

Don't think it would be the CV axles or transfer case as presumably all those parts are rotating if the transmission is in drive or neutral?

Hence, why I am perplexed. Thoughts?

[OilDripper]

No thoughts on this front end noise?

[E36M3]

There are two torrention bearings in the transfer case that is regular fluid changes are not kept up on cause spalling in the plates they ride against. Once the noise is there a fuild change isn’t going to do anything. Mine was fairly loud and annoying. Did a tear down on the transfer case to find the culprit. There is a company in Czech that sells the parts to rebuild it but I replaced it with a reman unit from overseas with a 2 year warranty and all is good. Could also be front diff or carrier bearing on the drive shaft. Carrier bear is easy to check. Just make sure you keep the splines aligned if you change it. I changed mine as it was worn out. Got rid of a very minor vibe I had that was intermittent.