Rear end noise (not fart) bearing or diff

[manydubs]

Are there any sure fire ways to determine what howling noise is?

I have a diff with freshly changed oil and no change in sound.

Both rear tires are highly worn out.

The noise sounds like a bearing, only starts around 30+ miles an hour and does not change whether I turn corners (put load on bearings from side) or engage the clutch, and accelerate or decellerate.

Thanks

[nicknikolovski]

A howling noise is usually a differential bearing problem and is usually present while accelerating quickly and then immediately decelerating because of the change of load on the bearings. But because you have said it does not change during these conditions I would say it would be a rear wheel bearing.

Listening to diff noise:
Jack the rear of the car and place it on jack stands. Choke front tyres. Then have an assistant get in the vehicle and start the engine. Place in gear and start releasing clutch and appling power to get the rear wheels spinning. If there is significant noise from the diff, then it most likely needs an overhaul or replacement.

Listening for wheel bearing noise (proberbly easier to do this on lift):
Jack rear of vehicle. Choke front tyres. Go to each rear wheel one at a time, spin the wheel by hand as fast as you can, then release it and allow it to free spin. You should hear a rumbling/whirring noise from bearings if they have failed. Also placing your hand on the back of rear wheel knuckle while the wheel is spinning you should be able to feel the runout of the bearing as it is moving.

[John W]

Did your rear tires wear out prematurely? Is there any uneven wear? Tires that are past their useful life can sometimes be noisy. ...

[manydubs]

They are just plain worn and evenly mind you.