2001 ranger scaping noise - not brakes

[zen]

Hello - I have a 2001 ranger 4.0 4x4 only 74k miles, factory auto(electric) hubs. I have a persistent scraping noise that has been bugging me for about the last 2 yrs. It sounds similar to disk brake sequel or grinding, most noticeable at lower speeds.
Other than the noise, everything works great.
I am about at wits end trying to figure this one out - I have searched web an forums and have not found anything similar.

Not a brake issue - I have replaced the rotors, calipers, pads several times, even the front hubs/hearings. About the only thing I can find which sounds even close is an old TSB for ford explorer saying there is a noise issue with the front differential axle seals. This is a $500 + job I dont want to have done if it is not really the issue.
Anybody else have this problem or a solid solution - thanks