Remove the drive shaft,turn the yoke to feel how much it takes to turn the differential a couple of turns,remove the pinion nut, Tap out the yoke and remove the pinion seal. I know I make the removal of the yoke sound easy( It can be a PITA) but it's usually not that difficult, some times it tskes rotating the yoke as you are tapping it out(yes jack stands or a lift are required for this...at least in my opinion.)
To reinstall the seal I've had good luck with a 2x4 block to get the seal in square and tap in the the yoke, Use a new locking nut or loctite the old pinion nut ,Bring the nut in slowly checking the fore and aft play of the yoke till you just get to the point of no slop,rotate the yoke and try to feel how much drag (bearing preload) there is,since the diff is assembled and the tires are still most likely still on It's tough to quantify what the actual bearing preload should be in Inch/pound measurements but if you bring the nut in till you get the same resistance you had before you removed the pinion nut you will be pretty close. Install drive shaft,Drive a short distance and if there are no new vibrations or noises you did good.
Teege
