I don't know if there is a "torque" spec per se on the pinion nut. If you go to Zuk's page at
www.gearinstalls.comHe always seems to crank the crap out of the pinion nut. What he ends up checking is the preload in inch-lbs. He has different values...I think it's like 9 or 10 in-lbs for new bearings, and less for used.