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

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20168/30=672

672x4.11x14/1001=38.6

devide 20168 by tire hieght then multiply ratio by that number then multiply drive gear by that number devided by 1001 gives you driven gear 34 to 45 are your choices

Assuming your speedo was right with the old gears, it's just a percentage thing. Count the teeth on your present driven gear and get one that's got correspondingly more teeth. Like, 3.00 to 4.00, if the old one has 12 teeth, you need one with 4/3 of 12=16 teeth.
Never had much to do with 400's. Can you just change the driven gear, or do they come as a set?
Oops! Had to edit . I went the wrong way! Lower gears need the speedo cable to spin slower, not faster. Duh!