speedo gears (help)

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Old 08-20-2011, 08:45 PM
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speedo gears (help)

I have a 904 trans with a 391 rearend, could anyone tell me how many teeth on the speedo gear would be correct one for the application?
Old 08-20-2011, 09:33 PM
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What size tires ? Probably about 38-39
Old 08-21-2011, 05:22 AM
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Gents -

Anybody have a chart for gear size relative to rear end ratio and tire size?

Tks

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Old 08-21-2011, 07:49 AM
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Mopar Speedometer Pinion Numbers
Axle Ratio Overall Tire Diameter

...........24".................... 26"................. 28".................... 30"
2.76 2538930(Yellow) 2538928(White) 2538926(Red) 2538924(White)
2.94 2538932(Black) 2538930(Yellow) 2538928(White) 2538926(Red)
3.21 2538935(Orange) 2538933(Yellow) 2838931(Green) 2838929(Black)
3.55 2538939(Green) 2538936(Red) 2538933(Yellow) 2538931(Green)
3.91 2538943(Blue) 2538940(Orange) 2538937(White) 2538935(Orange)
4.10 2538945(Yellow) 2538942(White) 2538939(Green) 2538936(Red)
4.30 2538944(Black) 2538941(Red) 2538938(Blue)
4.56 2538945(Yellow) 2538943(Blue) 2538940(Orange)

Last 2 digits are tooth count


Tire size calculation:

Tire Size: 245/60/15

245mm/25.4mm = 9.64 Inches Section Width

9.64 in. X 60% = 5.79 in. Side Wall Thickness

5.79 in. X 2 = 11.57 in. Total Side wall height

11.57 in. + 15 in. (Rim Size) = 26.6 in. Diameter
Old 08-21-2011, 12:02 PM
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340 -

Cool, tks!

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Old 08-21-2011, 08:52 PM
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I beleive that they are 235/60/14
Old 08-21-2011, 08:56 PM
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speedo gears for 391

I beleive that the tire size is 235/60/14. the car is at my buddies house so i can not check the size for sure. Thanks for all the replys.
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