What does differential hum sound like?

I'm trying to diagnose a new low hum coming from the back of the truck (2021, 67K miles). It's especially prominent at 60 mph. The pitch is low, like it could be coming from the exhaust, but the pitch is dependent on speed, not engine rpms. It seems independent of road surface type as well. I know that wheel bearings can also cause noise. Are the sounds different? Does a differential hum have a distinct kind of sound?

EDIT: I forgot to mention that my noise stays the same whether I'm drifting, slowing down, slightly accelerating, whatever. If I'm at 60mph the noise is there no matter what.

 

Diff noise is easily diagnosed through the use of the throttle pedal. At the given speed you have the noise occur, simple apply throttle or reduce throttle and see if the noise changes or goes away.

My diff makes the most noise with little to no load, when I am at a steady speed and the ring and pinion gears are just kind of floating lightly together. When I accelerate or coast to slow down a bit, the noise gets quieter until it goes away. For me it is around 80 to 100kph. Mine is light and never bothered me. 122,000kms and the diff is fine still. The oil looked new when I serviced it.


Edit: spelling mistake

 

I forgot to mention that my noise stays the same whether I'm drifting, slowing down, slightly accelerating, whatever. If I'm at 60mph the noise is there no matter what.

 

Tires if the pitch doesn't change with engine power or decel. What kind of rubber is on it? Miles on them?

 

You might have a bad wheel bearing.

 

They're Goodyear Wranglers - Territory AT, so not all that knobby, and they've never been noisy before. Not sure how many miles but not that many, maybe 10K.

 

Check out this video.

https://www.youtube.com/watch?v=Ni2JJi9yVxE

 

U said the sound is constant …how old are the tires ?

 

I agree with the others, if you hear the noise while coasting, then the noise is most likely not coming from your differential.

 

If it stays the same without load it’s tires or perhaps a wheel bearing. Turning the wheel will usually make a wheel bearing pitch change at speed for fronts. Jack up wheels and test those first.

My diff whine would be very noisy if I applied throttle on slight slope at 50-55mph. The TSB helped a little with the isolation pads, and sound deadening. It will not 100% remote remove the noise which is inherent to the design and variances of build.

 

Always sounded like more of a howl than a hum to me.

 

Like Michael McDonald backup vocals for a couple seconds.