Awhile ago diff fluid starts running down passenger tire, month later, passenger side axle shaft slides out while driving.
I replaced entire rear end with one from parts rig, noticed the next day it leaked oil on both tires.

Now about a week later i feel this axle is about to come apart, I think the passenger side has already started to slide out about a 1/4". Feel like its gonna pop off next time I drive.

What holds the axle shafts in and how is the oil sealed? What do I need to do to fix this? I have the manual but have never worked on a rear end.

Thanks