73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: farmallgray on November 13, 2008, 09:32:45 am
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I posted this on the FSC forum a couple weeks ago and didn't get much help, so I figured I would try it here;
I think somehow the rear output housing for my T-case in my 79 K-20 got swapped at one time along with the speedometer gears (don't ask how or why). The speedometer seems to be way off. I have 3.73 axles and I think the speedometer gears are for 4.10s. I know the gears are color coded. I can get some gears at work (NAPA), but I'm looking for a chart to pick the correct ones for my axle ratio and tire size. The NAPA book has a chart that lists "time seconds" to "tooth change" but that doesn't make any sense to me. Is there a chart somewhere online where I can figure this out?
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Try This
http://www.tciauto.com/Products/TechInfo/speedo_gears.asp
Once done with the Calculations, scroll down to your trans info, to find the gear best suited for you!
If you have further questions, TCI is great for answering about anything, even if your not buying anything from them(Great Customer Service!)...
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All the colors are listed here along with some standard calcuations:
http://www.73-87.com/7387garage/drivetrain/speedo.htm
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Or you could do it the easy way and go here http://www.transmissioncenter.net/speedometer_calibration_______va.htm (http://www.transmissioncenter.net/speedometer_calibration_______va.htm) and scroll down to the adapters. Figure out what percentage you are off by having someone either clock you or go past one of those radar displays that let you know your speed to get people to slow down. Then check and see if they have one that is close enough for you or you can do some simple math and get your self right on the money for an extra $10.