Use brake cleaner to clean the oil off the ring gear and use petroleum jelly to lube the bearings and the plastic gears that drive the speedometer. Also use petroleum jelly to lubricate the side plates.
Carefully re-install the carrier assembly into the case leaving the driver's side side plate out a little further than it's previous location based upon the markings we made before taking it apart.
It's time to bolt the pump which the pinion is mounted in to the differential case. You need to actually bolt it to the case. Washers have a crown to them. Be careful to orient the washer so the crowned side faces the pump/case so the outer edges of the washers don't scratch the pump. There's a special Subaru tool for turning the pinion which you'll see in my pictures but you could get by with a big wrench for this one.
To find the left/right positioning of the ring gear we tighten the driver's side side plate until the pinion won't turn any more. That is called the zero point. Then we back the driver's side side plate out 3 notches on the side plate. I end up with the driver's side plate one half notch further in than the last rebuilder did so I have less backlash.
To set the bearing preload we tighten the passenger side side plate until it stops turning, back it off, tighten it till it stops turning again, back it off, ...repeat..repeat, tighten it till it stops turning(meaning that it stops turning using the tool with one hand)...then tighten it 1 and 3/4 notches further using both hands. I end up 3/4 notches further in than the last rebuilder did so I have more bearing pre-load.
