Oil leak rear axle yoke

I have oil coming from the yoke on an 8.25 rear axle...

I understand a few things can cause this such as the oil slinger or the pinion nut...

What has happened when I noticed the oil is the vibes have gotten bad... So, is the leaking yoke a cause of vibes, or could the vibes be causing the leak>?

Also how much of a concern is it to be leaking, its nut pouring out.

The vibes and leakage are likely caused by something moving in a way that it should not.

grab the pinion yoke and shake it. vibes and leaking oil point to a bad pinion bearing that is wearing the seal.