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The shims are used to set the contact pattern up correctly. Shims are on the pinion as well, the combination is used to set the depth and backlash between the gears.

i know that there are shims on the pinion and behind the races of the carrier bearings i just wasnt sure if there were any under the bearing itself. i only plan on changing the carrier from a one wheel wonder to a limited slip

You should still check the backlash as it could be different with a different carrier. You will notice there is a little bit of play if you gently rock the two gears back and forth, that is the backlash. Ideally measured with a dial indicator but I do know people who just have a "feel" for how much play is there. You need a little play so the gears are not bound up which will also result in more wear. Just check your old ones if you haven't torn it apart yet as a comparison.