There is no shimming of anything needed. You remove the spider gears from the differential, and pull out the old clutches. You simply take the new clutches and reinstall them in the same order as the stock ones. There are clutches and metal spacers/shims that come out, is this what you are asking about? They are in some order when they come out: spacer-clutch-spacer-spacer-clutch-spacer, something like that. When I did it, I reinstalled them differently. By using one old clutch and the new set you can install them so it goes spacer-clutch-spacer-clutch-spacer-clutch-spacer. Or atleast something like that, I don't remember right now. The new order is supposed to increase friction so the differential has less tendancy to spin one wheel. Any ways, you just slide the combo of the washers and clutches back in, then reinstall the spider gears. That is it. It is very easy.