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#1 |
Registered User
Join Date: Nov 2012
Location: Salt Lake City, UT
Posts: 520
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Speedometer
I bought my 79 Silverado and the Speedo didn't work. I checked the cable and it was broken. I replaced the cable and went on a freeway drive today. This is what I was picking up:
Kinda funny. But I couldn't have been going more than 85 mph. Anybody know how to calibrate a cable speedo? |
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#2 |
Registered User
Join Date: Jul 2009
Location: washington
Posts: 4,178
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Re: Speedometer
The gears in the trans change your speedo info
Posted via Mobile Device
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377 sbc thumpr cam autogear m23 muncie 3:73 Detroit trutrac 3''spintech prostreet mufflers xpipe 1 3/4 headers build thread !http://67-72chevytrucks.com/vboard/s...d.php?t=577217 Iroc gauge threadhttp://67-72chevytrucks.com/vboard/s...d.php?t=554511 |
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#3 |
Parts and more parts
Join Date: Nov 2003
Location: Lebo, Kansas (middle of nowhere
Posts: 6,821
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Re: Speedometer
This website has a lot of info on what you need for speedo gears and from that you should be able to calculate what you need to make your speedo run right.
http://www.transmissioncenter.net/sp...FS-oPAodO3wA_Q
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Frank |
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#4 |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
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Re: Speedometer
Several years ago I put together a spreadsheet to calculate some "what ifs" for axle ratios and tire sizes. RPM_Gear_Axle_Transmission_TransferCase.zip
The sheet calculates ideal speedo gears based on tire size and axle ratio. Rows 50-100 are the speedometer info. Modify the blue numbers in rows 6-11 to match your axle ratio and tire sizes. The sheet also calculates RPMs at various MPH based on tire size, transmission ratios, and rear axle ratio. Change the red numbers in M8-M14 to match your transmission ratios.
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And please let us know if and how your repairs were successful. |
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