I'd hope it wouldn't be the axle bearing on that side, but if there is noise or slop there, the seal could have been torn by excess play. I'd also check the top breather/vent hose to make sure it's not plugged. A plugged vent will cause the diff housing to build pressure and blow oil out the axle seals. The axle seals themselves are replaceable from the outside. They look real easy to R/R.
Joel