I was told that the factory uses a numbering system to identify the shims for their pinion depths on their gears. I'm unable to find a chart that identifies what their number stand for. Anyone able to help? Also, I'm adding a detroit locker in the rear. I seen some old post that stated not to use synthetics with a detroit locker. The instructions stated to use whatever the factory recommends. Jeep recommends synthetics for towing. I don't use my jeep for towing, but figured the pressures on the gears would be similar when off roading with 35" tires and 5.13 gears. Any advise? Thanks for the help.