2004 F250 5.4 4WD 10.5 Sterling. I am hearing what I would describe as a consistent rhythmic whirring at all speeds, acceleration/deceleration, braking/coasting and so on. I can’t seem to make the sound change in severity, only in speed when slowing down or speeding up. I have replaced all 4 wheel bearings, calipers, pads, rotors, backing plates and installed warn manual hubs.
Would an issue with the rear diff be consistent with these symptoms? I feel like load would make the sound change so I am unsure where to go next.
I replaced the parking brakes 18 months ago along with the rear dust shields/plates.
Any help or pointers on where to go next is greatly appreciated.
-Colin

 

A carrier bearing (if your truck has one), or a bad pinion bearing will make constant noise, changing with speed.
Jack the back end up, and spin a tire by hand (may have to block the opposite tire, so that the driveshaft will turn), and listen.
You may be able to pinpoint where the noise is located.