Re: 12 bolt rearend leak
Mark the pinion and nut with a ***** punch. Count threads. Yank the nut, washer, and yoke. Replace seal. Put the yoke, washer, and nut back on. Tighten the nut down until it is just barely past the mark you made with the ***** punch.
Ideally, you want to check the pinion bearing preload but that involves a lot of work.
Don't forget to mark which universal cap went into which part of the yoke. Be careful when removing the old pinion seal, you don't want to damage the sealing surface on the pinion shaft.