I had the following work done on my 2001 Expedition 5.4L January 2007:

Front Brake pads, Front brake rotors, Wheel bearings repacked, replace front grease seals
Rear Brake pads, Rear rotors turned
Rear Axle Seals replaced both sides
170,200

Now (230,000 miles) I'm getting a slight grinding noise from the rear end. Ford Dealership has told me I need a rear axle rebuild ($1900). I've never had a vehicle with this many miles on it that needed this kind of extensive work. What about simply replacing the differential fluid?? I dont believe the Dealership took the "pumpkin" off to examine the gears for shavings and there does not appear to be any leakage under the rear axle onto pavement.
The grinding noise is very obvious at low speeds, but not at higher speeds (over 30mph).

thanks for the help, guys!

 

At 230,000 I wouldn't worry too much especially if it is slight. Go ahead and change the fluid and drive it until it gets worse. It could make that noise for another 230,000 before it fails. The repairs will cost the same no matter what.

Wojo

 

I took my 2001 Expy to another mechanic and they have diagnosed the problem as a flat spot on the bearing inside the differential. A rebuild job was estimated to be $1400.
Thanks for the above advice as I will be driving it a bit longer. The noise is not yet bothersome.

 

Better bring it to a 3rd mechanic because this one got it wrong too. Flat spots on bearing cause clicking not grinding sounds.

It's been 60,000 miles since you had the brakes done. I would be more inclined to think the rear grinding noise is a brake problem and not a differential one.

Have to tried to use your parking brake lately?

 

Thanks on the 3rd opinion. It's been a guessing game with the mechanics involved. . (Ford Dealership and Tire and Wheel repair shop). I do use the parking brake 80% of the time and it's working good. The Tire and Wheel shop took all the tires off and inspected the rotors (I watched), but it could still be a brake issue since they didnt disassemble anything, only visual inspection.

 

The reason I asked about the parking brake is because it is hidden. You cannot inspect it unless the rear rotors are removed. Rust and other gunk likes to build up in the parking brake area and can be a source of grinding noises.

Sometimes while moving slow (10-15 MPH), if you apply the parking brake and listen, you can hear if the grinding noise changes. If it does, the parking brake is a likely source for your noise. Myself...I do this once a month anyway just to help keep the PB areas clean.

 

Front wheel bearings need replaced .. but i can't tell if this noise is coming from them or not. It really sounds like its the rear of the Expedition instead of the front. $300 for front wheel bearing work (both sides).

 

Front wheel bearings were replaced today and some vibration was fixed. Mechanic diagnosed the rear axle bearings as making the noise in the rear. A total rebuild is soon coming.
Note on the Front Wheel bearings: Shop that did them before didnt pack the bearing right and it almost cost me a spindle (big $$$). I got both wheels done for $239.

 

Rear axle was cleaned out and totally rebuilt. Nice and quiet ride now! Carriage bearings were worn and making the noise.