Ring and pinion replacement

I plan to replace the ring and pinion in a D30.
The pinions have a shim number etched to help with the shimming
of the pinion.
If I use the FSM conversion chart and shim it based on the pinion numbers, what's the chance that it will be correct the first time?

I would say about 10%. It will get you close, but rarely spot on.

old_man said:

I would say about 10%. It will get you close, but rarely spot on.

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Too bad! I was hoping it will be simple. So, I set it up with the shims according to the numbers on the pinions, set the backlash read the pattern, add/remove shims and repeat. How many thousands each time on the pinion?
Any shortcuts?
Thanks.