Same sound on test drive ..How do I uploads video ?
Im gonna rule out tires 1st..

Have to host your video elsewhere, and then just link to it here.

Yep, thats the vent hose. I don't think its a valve on the end though, I think its just a breather cap.

How long was that fluid in there?

Is there a oneway valve at the base area to allow air out but not bk in?
A few years ago I replaced the entire rear .an changed it then..maybe there was gunk in the Axel area.
Im getting tthe video link...low churn like .maybe tire?
No change as turning just hear more as going faster..less at 30mph but still there,more at 50 an up..


https://youtu.be/pF6Tj33AU_w?feature=shared

Run it with the rear up on jack stands. That should remove tires from the equation. Usually when a diff is going, it's more of a high pitch whine, at least that's my experience. Maybe with it up on jack stands you can pinpoint a bit better. Just don't get caught by the wheels! You can also take the wheels off and see if the sound changes.

Is that a wheel or maybe a tire sound to u?

Like I said, in my experiences, diffs make a high pitch whine on the way out. Hard to say what else could be the cause. Jackstands, cardboard, get under it and listen is my suggestion. Have someone gas it for u.