# speedo gear calculation



## deanhickey (Apr 6, 2015)

I need some help. I have been trying to find out how many teeth my driven speedo gear should have. These are the numbers:
tire diameter:25.10
Revolutions per mile:803.5
axel ratio:3.36
dive teeth:5 
tire size235/60R14
Transmission: Turbo 400

My calculation is: 5x3.36x 803.5 divided by 1001 =13.4

the gear holder is a 40 series it has the making on the outside and the gear that was in it was a yellow 41 tooth gear.
(I have a photo of the drive teeth but I get invalid file when I try to up load.)

What am I missing

Thanks,
Dean


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## deanhickey (Apr 6, 2015)

deanhickey said:


> I need some help. I have been trying to find out how many teeth my driven speedo gear should have. These are the numbers:
> tire diameter:25.10
> Revolutions per mile:803.5
> axel ratio:3.36
> ...


Correction the Drive gear has 16 teeth. that gives me a driven gear of 43 teeth.


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