How to perform speedometer calibration

[dave]

I often wondered about if a customer walked into your shop and requested a speedometer calibration (probably because they just received a speeding ticket) how to perform this procedure? I was never taught how to do this in school. Any ideas?

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[Daniel]

I have never heard of this. I googled it and found a few special tools for it. I wonder if the Snap-on scan tool at my shop is capable of this.

[Bill]

I used to check them on a chassis dyno but i never calibrated one. If the tire size was correct i just replaced the speedometer. A few times i found the wrong drive gear installed on the speed sensor or cable drive but with newer cars i don’t see that much anymore.

[Daniel]

I asked one of the more experienced guys at my shop and he said you can re-calibrate alot of trucks made after 90ish to compensate for tire or gearing changes. Federal law will not allow any change to the odometer though.

[Author]

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