leaking pinion seal

any tips on changing the front seal on a 489 centre section?
index and change or re torque to 180lbs.

I watched a youtube video where they pointed out that if you're worried about the pinion bearing preload, you can count the number of threads exposed and mark the nut and tip of the pinion gear (making sure you don't wreck the threads). Make sure you index the yoke the same way. Torque it to about 100 LBS to start, then walk it in slowly until the same mark line up.
mike