# Speedometer gear in trans



## ronrandltsi (Sep 14, 2020)

does anyone know how many teeth the speedometer gear has in the trans of 1969 gto with 4 speed , 355 geaars and 3.90axle ratio


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## GTOTIGR (May 3, 2020)

Hi,
The variables related to your question are numerous. While not scientific, you can purchase inexpensively on eBay or many other places a selection or “driven” gears and experiment. There are numerous mobile phone apps that accurately gauge your speed so you can determine if the gear you put in the bullet housing results in your speedometer matching the speed on the app.


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## Mine'sa66 (Oct 30, 2019)

GTOTIGR said:


> Hi,
> The variables related to your question are numerous. While not scientific, you can purchase inexpensively on eBay or many other places a selection or “driven” gears and experiment. There are numerous mobile phone apps that accurately gauge your speed so you can determine if the gear you put in the bullet housing results in your speedometer matching the speed on the app.


I think what he might be hoping to find out is what tooth count it came with so he can do the math and buy just the one he needs.
I don't think it's answerable since he states it has both 3.55 and 3.90 gears.
To the OP...keep in mind, the speedo gear that was used assumes the stock tire height, so make sure you calculate that in.
I need a speedo gear change too. The kits I see are all nearly $100 for the whole assortment. I'd rather do the math and buy just the one I need as well. Since mine is almost exactly a nice even 20% off, and I have a degree in mathematics, I just calculate as I go


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## Jared (Apr 19, 2013)

Maybe this will help?






TCI Speedometer Gear Calculator


Leading provider of high performance automatic transmissions, torque converters and drivetrain components for race, street/strip, hot rod, street rod and towing




www.tciauto.com


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