My car was up on the hoist today for a new exhaust, and I noticed that the seal on the right side of the diff casing, where it meets the output shaft, seems to be leaky. It's all covered in oil. The left side is fine.

Is this a common problem? An easy fix? Sorry, I might have got some of the terminology wrong, but I think you know the place I'm talking about. If not, I can take a pic.

Thanks.