Rhythmic humming noise at 40 mph

Makes sense because the hub bearing is going from a driven to a drive unit. But there is an applicable technical service bulleting from Ford that you should see if it applies to your vehicle. Another common failure point is the integrated wheel end units (IWE) at the wheel hub area, and or a faulty vacuum line. a real good visual inspection as well as verifying the presence of vacuum and no vacuum when commanding 4x4 on and off. There should be a constant vacuum at the IWE with the vehicle in 2wd, and no vacuum in 4wd.

That's awesome information, thanks so much. I picked up some Detroit Axle hub assemblies. Are they a reputable manufacturer?

Good morning,

Yes, those hubs are a good brand.

I attached the procedure and a picture for you for the procedure.

https://www.2carpros.com/articles/bearing-hub-replacement

Please let us know if you have any other questions.

Roy

Removal and Installation

CAUTION: Suspension fasteners are critical parts because they affect performance of vital components and systems and their failure may result in major service expense. New parts must be installed with the same part numbers or equivalent part, if replacement is necessary. Do not use a replacement part of lesser quality or substitute design. Torque values must be used during reassembly to make sure of correct retention of these parts.

1. Remove the wheel and tire.
2. Remove and discard the halfshaft nut.
To install, tighten to 27 Nm (20 lb-ft).

3. CAUTION: Do not allow the caliper and anchor plate assembly to hang from the brake hose or damage to the hose can occur.

Remove the bolts and position the caliper and anchor plate assembly aside.
Support the caliper and anchor plate assembly using mechanic's wire.
To install, tighten to 200 Nm (148 lb-ft).
4. Remove the brake disc.
5. If equipped, detach the wheel speed sensor harness clips from the brake hose.
6. If equipped, remove the front wheel speed sensor bolt and position the sensor aside.
To install, tighten to 9 Nm (80 lb-in).

7. CAUTION: Do not use a hammer to separate the halfshaft from the hub or damage to the halfshaft can occur.

Remove the 4 wheel hub bolts and the wheel bearing and wheel hub assembly.
Discard the bolts.
To install, tighten to 200 Nm (148 lb-ft).

8. CAUTION: To prevent halfshaft or hub damage, verify the spline engagement by checking for spline lash before installing the halfshaft nut.

To install, reverse the removal procedure.