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Old 05-03-2005, 01:12 PM   #1
phanatic32212
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Speedometer Calculation

Sorry for the long post, but this don't sound right to me and I know one of you guys will know. I've looked almost everywhere on the net and I can't find what I am looking for. I need to find my true speed based on rpm and gear ratio. I have 3.07 rear with th350 tranny, and at 3200 rpm the speedometer reads 71. I am running a 26.4 tire (295/50/15) in the back and 235/60/15 in the front. I had a friend drive next to me and give me a thumbs up @ 60 mph. At 60 mph this is all of the info that I had.

Thanks in Advance
JAke
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Old 05-03-2005, 01:25 PM   #2
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Try this one.
http://www.angelfire.com/fl/procrastination/rear.html
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68 build thread
http://67-72chevytrucks.com/vboard/s...d.php?t=223234
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Old 05-03-2005, 01:31 PM   #3
phanatic32212
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That one says 81 mph and I really don't think that is right. I have a posi unit, that wouldn't have anything to do with it? The numbers stamped on the ring gear is 14:43. <-- 3.07, right?
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Old 05-04-2005, 01:19 AM   #4
ryanroo
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at just over 2500 you should be going 65, 2150 is 55mph, 2350 is 60, 71 is 2770
ryan
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