Rear end problem help

Well see how it turns out but I'm curious on my axle bearings possibly causing the humming, let me know if I could be wrong about what I'm about to say.

When I bought the rear end assembly with my other center section it was all together drum to drum. Well all I did is slap it in the car and just did a quick check of the brakes and everything looked good...to so I thought. Well when I decided to put the car on the lift last week and inspect a couple things I found that the axle bearing adjuster tab that holds it in place was never on it....so the bearings must have been tightening and loosening constantly and I'm wondering if it wore out a bearing for the time being(I didn't check bearings either when I last pulled out the axles cause I was running out of time) and thats where I'm hearing this howling noise? Idk if this is a possibility but that's why I do want to pull the axles and check but will I have to worry about any gear fluid coming out?

And I know that was a bad mistake but is this plausable?