Unusual Noise

[04exped]

I have a 2004 expediton 5.4L
there is a noise coming from underneath of it, its not real loud as in the guy next to me can hear it. Initially i thought it was the hub bearing and so it went to ford dealership and the said it was the right front hub bearing. I replaced it but the noise continues. I am told that it may be the front differential but how does it go bad? I was considering disconnecting it, but by the wheels still being connected i don't think it would do any good.

Any suggestions?
i am new to the site and just looking for help.

 

[metaldrgn]

Need more info. Is this noise just occurring while in motion? At a certain speed? Can you describe the sound?

 

[GAINMOB]

do u have air suspension? what does it sound like?

 

[04exped]

no air suspension.
the noise is more like gears turning, like and air plane eeeeern??
at 20 mph is when it starts and continues. only when in motion although i have not tried it in reverse.

 

[metaldrgn]

Could be a wheel bearing then. There was someone else who had a similar problem, maybe search for it, and it ended up being a rear wheel bearing. Differentials will start whining when they don't get proper lube (that's the primary reason anyhow).

Does it sound like a whining or more like a grinding noise?

 

[04exped]

Hope this helps someone else
it turned out to be the front diff gear box.. and the electronic component that uses a vacuum i believe to engage and disengage 4 wheel drive. i really hope this helps someone else.
the noise is completely gone now..