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Old 12-27-2003, 12:46 AM   #1
67chevytodd
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Question M-20 speedometer gears

I have a 67 C-10 with a Muncie M-20 4spd tranny. I have changed the rear end from a 3:73 to a 3:07. The tranny currently has a 19 tooth steel one piece gear. I will be using 235/75/ R15 (29 in dia.) tires. What speedo gear do I need to change to, and where do I get them. The two GM dealers that I went to do not have info that goes back that far. Please help! Todd
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Old 12-27-2003, 01:04 AM   #2
cwilli84
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Go to TCI s transmission website they have lotsa good info to get you going in th right direction.
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Old 12-28-2003, 05:21 AM   #3
jimfulco
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My '79 Suburban with 3.07 gears & 29" tires (255/70-15) had a 9-tooth drive gear & a 20-tooth driven gear. The speedo matched the local police radar trailer at 50mph. My old M-20 had an 8-tooth steel drive gear, but I've never seen one with 19. An 8-tooth drive gear with an 18-tooth driven gear would be almost the same as my Sub. Check these sites out:

www.novaresource.org/speedo.htm
www.novaresource.org/speedo2.htm
www.tciauto.com/tech_info/speedo_gears.htm

Last edited by jimfulco; 12-28-2003 at 05:33 AM.
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