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Speedometer Gear Requirements Here's how you do it....you need to know two things. The rolling circumference of the rear tires (don't use the diameter), and the rear end gear ratio. For the sake of this example we'll us 3.27 gears and tires with 85 inches per revolution, 275-60-15 Goodrich T/A's. We will assume your Tremec TKO has a 7 tooth drive gear in it from the factory. Inches per mile: 5280 x 12 = 63360" per mile Tire Rotation per mile: 63360/85 = 745.41 Rotations per Mile Driven gear teeth: (Drive gear teeth X axle ratio X tire revs per mile) / 1000 (7 X 3.27 X 745.41) / 1000 = 17.06 According to the Ford Performance Parts Book a 17 tooth driven gear is "white" (C3DZ-C). We divide by 1000 because Speedo manufactures build their speedometers to expect 1000 turns of the cable per mile driven. This should help you sort out the required gear on the end of your speedometer cable. we have speedometer gears available is a kit form with several sizes to help you get your speedometer close to accurate! 45$ per kit and it includes the gear clips too! George This link came from Club Cobra 8/24/02 speedo_gear_select RPM TKO-600 Calculator
09/15/05 |