I have had luck in the past with putting a witness mark on the pinion nut and shaft so that you can return the nut to approxamatly its original bearing load.
The proper way would be to take it all apart and set the rotational torque in inch pounds at the correct setting for used bearings ,but the mark and return method works pretty well for me.
You will want to make shure to back up the pinion ,not just throw a wrench on there and snap ring teeth off,there should be a place to get a wrench on there to hold it and leave room for another wrench to take off the nut.
The same principal with removing a plumbing fitting ,back it up.i had to use a large pipe wrench on the last one to back up the pinion for the nut removal.
Also at a minimal use blue loctite when re-installing the nut ,you should actually use a new nut too and i think it calls for red loctite on a new nut.........old nut is not recomended for re-use.