Thread: How do I figure which speedometer gear drive I need after I change rear end ratios???

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Sometimes you have to change both gears to get the proper pitch so they mesh. A good speedo shop should be able to help you,as most dealerships haven't stocked parts for turbo 400's in quite some time,but they did have charts to show which gears worked with the other,they were color coded. Hope this helps you,Hank

I just change my [ 350 trans. ] chevy , gears to 373 . I had to change both drive and driven gears. Drive gear teeth = 7 and Driven gear teeth was 20 .

Lots of calculators here.

http://www.wallaceracing.com/speedo-calculator.php

Jud