67-81 Camaro Trans Am Saginaw Muncie PG TH350 Speedometer Gear 21T Teeth RED A

67-81 Camaro Trans Am Saginaw Muncie PG TH350 Speedometer Gear 21T Teeth RED A
    Code: ATP-YA17
    Price: $8.58
    Shipping Weight: 0.19 pounds
    1 available for immediate delivery
    Quantity in Basket: None
    New ATP speedometer gear. This is a 21 tooth (red) plastic gear. This will fit Muncie, Saginaw and Powerglide transmission, also TH350 but ONLY with a 1" OD gear housing (where the o-ring sits). This will not fit the 2" housing, nor TH400/700R4. Please be advised that proper speedometer calibrations are based on differential gear ratio and tire size (overall diameter), and need to be calculated properly. If you are not sure what you need, please contact us prior to ordering! Fits the following:

    67-81 Camaro
    67-81 Firebird/Trans Am

    CALCULATION : To calculate the gear tooth count you need if changing rear gears or tire sizes, you will need to closely match the ratio of the 2 transmission driven and drive gears to the ratio of the rear ring and pinion ratio and tire diameter.

    You can use the formula : SPEEDO GEAR RATIO = (DIFF GEAR RATIO x 20.2 / TIRE DIAMETER)

    EXAMPLE : 3.73 Gears x 20.2 x 25.6" (245/50R16 tire) = 2.94 speedo gear ratio. Closest match for a 2" housing would be 44 tooth -15 tooth (2.93 ratio), closest match for a 1" housing would be 21 tooth -7 tooth (3.00 ratio). The closer the speedo gear ratio is to the gear/tire size calculation, the more accurate your speedometer will be. Be advised not every ratio can be matched perfectly, as there is no 20.58" speedo gear made (in this example), you would select a gear closest to the calculated ratio.