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Old 11-05-2019, 03:36 AM   #1
american revolution
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fix for speedometer reading wrong due to new 700r4

any help, installed a 700r4 transmission in my 64 c10...speedometer seems a little off now..feels like i'm going 65mph and speedometer showing 100mph..

heard that i need to get the gears changed on the speedometer cable...how can i figure this out and where do i search to get the correct gear?
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Old 11-05-2019, 07:35 AM   #2
rpmerf
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Re: fix for speedometer reading wrong due to new 700r4

You can find gears here:
https://www.rockauto.com/en/catalog/...ive+gear,11676

https://www.summitracing.com/search/...ion-type/700r4

short how to:
http://www.73-87.com/7387garage/drivetrain/spdgears.htm

calculator here:
https://www.tciauto.com/speedometer-gear-calculator

Also, if you have a smart phone, you can download a GPS speedometer app and verify accuracy.
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Old 11-05-2019, 07:43 AM   #3
PGSigns
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Re: fix for speedometer reading wrong due to new 700r4

Here is what you need to know. Tire height, rear end ratio and the color of the drive gear in the transmission. Then you can go to tone of the gear calculator pages and find out what driven gear you need. You may find that the drive gear will not work for your setup and have to change it. I have linked TCI's page below and they have a list of available drive gear options for you trans listed. You can try drive gears with more or less teeth till you find a set that works for your truck.
Jimmy
https://www.tciauto.com/speedometer-gear-calculator
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