Depth gauges are used to determine the shim stacks for both: pinion & ring gears. Then, a drag check is done to both independently. When reassembled, blue is used to verify gear print. Box is again reassembled after cleaning the blue and the backlash is recorded. If all parameters are within speck, the final drag check of a compleate assembly is done. If you're lucky, the gearbox will be dissassembled & reassembled only three times during this procedure. This is not from MB, this is how Robinson R22 & R44 helicopter main & tail gearboxes are done.