My new to me 2018 screw 4x4 has a low frequency droan from the front end that gets worse as fluids warm up. The left IWE, hub and bearing have been replaced. No improvement to droan, but clunking is gone. Shifting to 4 auto causes the noise to go away after a few seconds, but can come back if on/off gas. This is pass 1 by the dealer and they are willing to look further. Has anyone else experienced this and what was the solution? I'm trying to avoid multiple appointments.

 

Vacuum leak on the actuator? Check and make sure the hose is seated properly.

 

I'll give it a look.
Thanks!

 

If you don't have the latest vacuum valve, which is blue, I'd buy one. It's less than $10 delivered. Cheaper than your time and/or gas having to deal with a dealer. Good luck.

 

When you shift to 4A, the IWEs will lock in, so I'm not thinking a vacuum problem. You say it still drones off/on in 4A with on/off of the gas. Bad CV? Something in the front diff? I'd have the dealer check it out further.
Does it still do it in 4H?
Try pulling the power on the solenoid to lock in IWEs, and drive it in 2H, trying to isolate the Transfercase right now.Try pulling the power on the solenoid to lock in IWEs, and drive it in 2H, trying to isolate the Transfercase right now.

 

Not to argue but they do not lock when in 4A but rather until the truck determines that 4WD is needed and they they lock in, that's the whole "AUTO" thing.

And if you really want to test the actuators all you have to do is pull the vacuum line from the actuator off.

Either way, Johnday is absolutely correct, take it back.

 

Thanks for the input.
When I shift to 4 auto, the noise will go away. Sometimes immediately, other times it might take a few seconds. When in 4 auto it will sometimes come and go when I'm on/off the gas. When in 2wd, noise is constant regardless of throttle. I haven't tried 4H since the IWE was replaced. I'll try today.

 

This is incorrect - they DO lock in when in 4A and the transfer case controls the front to rear torque proportioning (TOD).

 

You guys might like to see this, if you haven't already. He's describing how the Tcase works, doesn't matter if it's a Raptor or not, it's the same TC if you have 4A.
Ford F-150 Raptor 4WD Explained - Raptor Has 4WD and AWD

 

Interesting, and that would actually make more sense. Thanks for the info!