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Discussion Starter · #1 ·
I am changing the gears in my 1985 jeep cj7 dana 30 and amc 20 the new pinion is maked 2.559 not + or - . The standard depth for a amc 20 is 2.547 this would lead me to belive that the pinion is +12. Is this correct. If so sould I send it back.Acording to the service manual I souldn't youse any thing beyond + or - 9. Is this correct.
PLease Help
THanks Brian
 

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just used the old shims. If you destroyed them taking the pinion out then measure the shim thickness and start with that amount. This is only a starting point any way.
 

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In my limited experience:
Ring and pinion are generally made as a set so that easy installation is possible by following the new sets measurements.
Since you use the term "gears" do you mean you bought a set and are replacing both. If so go by the measurements on the new set. Use the normal backlash setting along with the preload. If your preload is difficult with the new gears you can warm the pumpkin with a torch to make it expand.
The real test will be: tooth mating surface test with blue dycum. Also check for smooth runing by handing turning after assembly. Use a light machine oil as a test lubricant.
 

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Discussion Starter · #4 ·
yes I am Replacing both the ring and pinion. But acording to the service manual you souldn't shim more than .009 I think I would need .012 to get it to factory sepecs I relize from this
I would have to adjust for proper backlash and pre load but this may have move me to more than .012 in shims.
 

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Factory specs are stated based on what the factory accepts from various manufactures. The incoming parts must meet a certain range of measurements. Hence the MANAUL is written.
Now you have bought a set of gears from a out source and they have given measurements for you to follow. A 12thsnds on a new set of gears is well within the range of a rebuild with out using stock gears. AS long as all the other measurements are met where stock parts are used. The above specs to meet are the preload on the bearings and the tooth mating test. These two specs change with heat while you are running. To tight or too loose equals a second rebuild. or $$$$$$$.
 
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