Yes, Gear Contact Pattern is the right term,
but this does not change unless you are changing
the Ring & Pinion gears too. Contact Pattern is
changed by the depth of the Pinion.
Back Lash is the distance, measured in Thousanths
of an inch or mm that the ring gear turns (moves)
while the pinion is held still, it should be around .008
of an inch (eight thousanths of an inch) and is measured
with a Mag Base Dial Indicator.
This is changed by rotating the ring that has the holes in it,
just make sure you loosen or snug both rings evenly, and
that they are tightened to keep the slop out of the bearings.
Good Luck
Wild