Hum from rear starts at 25mph

[VA-Mach1]

Hi everyone. My 2002 Explorer XLT 4X4 developed a hum in the rear. Just seemed to have started one day. I did not notice it getting louder. Don't think it's the wheel bearings. I have already been though bad rear wheel bearings. They hummed a lot louder and would get louder or quieter going around a left or right corner depending on which side was bad. The rear diff was rebuilt at the same time when the wheel bearings got replaced. This is a steady hum that starts at 25mph every time. Does not matter if I am on or off the throttle hums the same. Never replaced the half shafts and have 226K on it. Everything I read about half shafts say they clunk and bang. So I'm leaning toward the rear diff even though it was rebuilt.

Any thoughts?

 

[imp]

Hi everyone. My 2002 Explorer XLT 4X4 developed a hum in the rear. Just seemed to have started one day. I did not notice it getting louder. Don't think it's the wheel bearings. I have already been though bad rear wheel bearings. They hummed a lot louder and would get louder or quieter going around a left or right corner depending on which side was bad. The rear diff was rebuilt at the same time when the wheel bearings got replaced. This is a steady hum that starts at 25mph every time. Does not matter if I am on or off the throttle hums the same. Never replaced the half shafts and have 226K on it. Everything I read about half shafts say they clunk and bang. So I'm leaning toward the rear diff even though it was rebuilt.

Any thoughts?

@VA-Mach1

Rebuilt how long ago? If very recently, improper ring and pinion tooth contact pattern. imp

 

[dla]

Hi everyone. My 2002 Explorer XLT 4X4 developed a hum in the rear. Just seemed to have started one day. I did not notice it getting louder. Don't think it's the wheel bearings. I have already been though bad rear wheel bearings. They hummed a lot louder and would get louder or quieter going around a left or right corner depending on which side was bad. The rear diff was rebuilt at the same time when the wheel bearings got replaced. This is a steady hum that starts at 25mph every time. Does not matter if I am on or off the throttle hums the same. Never replaced the half shafts and have 226K on it. Everything I read about half shafts say they clunk and bang. So I'm leaning toward the rear diff even though it was rebuilt.

Any thoughts?

Gotta put all 4 wheels in the air. Have a helper run it up to 30mph while you listen (stethoscope, big screwdriver, etc.). There's really no other way to diagnosis a "humming" sound.

 

[VA-Mach1]

I ended up pulling a rear carrier from the junk yard and switched it out. Took care of the problem.