When I checked the rear end oil on my rubicon it was dry so I filled it up just to watch it all run down the inside of my left wheel the next time I rode. The rear end makes a funny noise every once and awhile so im wondering if I need to replace the bearings or just the seal to stop the oil leak.

 

What your seeing is a failure of the seals. Both internal and external. But you can almost be sure that if the seals are shot, then the bearings are shot also. Even if they aren't you might as well replace them as long as your in there. They aren't expensive.