12 bolt differential pinion seal replacement

[David67]

67 c10, 292, 12 bolt rear differential. The pinion shaft seal is leaking badly, but our manual doesn't really say how to torque the nut after replacment of the seal. (Bearing MAY need replacing...not sure yet).

Any guidance/tips would be hugely appreciated. How critical is the nut torque? Some other blog said something about pinion bearing wearing out if not done properly, but no help on just what "properly" was.

Thanks in advance.

David