I did this job last fall. I tried it the shortcut way and it all went out the window when I discovered the loose pinion nut. The ref marks were useless because it referenced the loose nut! So now I knew why my pinion seal was failing. I can't imagine doing this from underneath the car. I would take the interior out. It is not that bad of a job. I am just getting around to putting it back in. I drove it up till winter with the interior out (except for the seats of course). I put 200 miles on it and the rear is as dry as a bone. It even has dust on it!!! No noises or acting weird in any way. I was very unsure that my makeshift procedure would work, so I drove it for a while because I did not want to remove the interior twice. I even took it past 110 mph a few times.
So ended up actually going 180 deg past the staked position of the nut. I used an inch lb Toque wrench to establish and benchmark drag torque (loose nut). I call this the zero or unloaded number. Then I added the number Patrick posted. In other words, if my unloaded number was 15 in lbs, then add the 30 in lbs, my final figure would be 45 in lbs. In essence, this would have been 30 lbs because the 15 doesn't count
Cleanliness is huge when re-installing. De-grease threads thoroughly and use red lock tight on nut. I also use some RTV on the threads on the other side of seal to prevent seeping
oil from the threads.
Here is the thread started at that time. Hope it helps.
Finally attempting to tackle that leaky rear
Dave