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| | | Joined: Mar 2017 Posts: 53 'Bolter | | 'Bolter Joined: Mar 2017 Posts: 53 | In my 49 GMC I am using the original speedometer with a 700r4 trans. The speedometer reads approx. 68 when I'm going 60. And the odometer reads 6.5 miles traveled when I have actually gone 5.
The trans has a blue 38 tooth driven gear and a greyish drive gear that I can't count the teeth on.
I read somewhere that each tooth change on the driven gear will change the speedometer reading by 2 mph. More teeth slows the reading and less teeth increases the reading. If this is correct then I would need to install a 42 tooth driven gear. Does anyone know if the grey drive gear can handle the change to 42 or do I need to change the drive gear also? and if so to what and then what driven gear would I use as this would change the overall ratio.
Does anyone know what rpm the speedometer shaft has to turn to have the speedometer read 60mph? This might help me sort this out.
Tom | | |
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