I pulled the yoke in preparation to change the pinion seal. I had a slow leak that was I was tired of. Unfortunately, I found a groove on the yoke.
Picture:
http://i50.tinypic.com/357frjq.jpg

Am I right in assuming that that grove would allow the gear oil to leak out? The pinion seal appears to be in good shape, so I don't think that is to blame.

Pinion seal:
http://i50.tinypic.com/wahi83.jpg

What would have caused that groove to form in the first place?