05-28-2017, 04:58 PM | #1 |
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Speedo gear
My speedometer is off by 5 mph when I reach 35 + mph. Slower speeds its still not accurate. It's a stock 31 with 19 in tires. Where do I begin to see if I have the right gear? By looking in the catalogs I need to know what gear ratio I have. Isn't there a way by jacking up the rear and turning the wheel to find the gear ratio? Can you explain how it is done.
Thanks
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05-28-2017, 05:02 PM | #2 |
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Re: Speedo gear
hmm its going to be a bit tricky but put the car in 3rd, jack up one wheel, and mark the tire - then count how many times you need to hand crank the engine to get the tire to rotate one revolution. like a ratio of 3.54. Its really 3.54:1 meaning it takes 3.54 turns of the input(driveshaft) to get the output (wheel) to turn one revolution.
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05-28-2017, 05:17 PM | #3 | |
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Re: Speedo gear
Quote:
Charlie Stephens |
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05-28-2017, 06:05 PM | #4 |
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Re: Speedo gear
Okay how do I check my speedometer for accuracy ?
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05-28-2017, 06:14 PM | #5 |
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Re: Speedo gear
I had tried some of those roll the car or lift one wheel and crank the engine by hand..
I finally jacked up the rear end, removed the fill plug, cleaned one of the ring gear teeth with a swab and marked it...then turned the rear end one tooth at a time and counted the teeth....I'm not sure if you could see the mark if the rear end were full 34 teeth you probably have a 3:78 to 1 other ratios here. http://www.fordgarage.com/pages/rearaxleratios.htm I used a hand held GPS to check speedo accuracy.....I realize you may not have one....
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05-28-2017, 06:22 PM | #6 | |
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Re: Speedo gear
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Quote:
Thanks for the chart that shows me the different gear ratios. That will be the best way to see witch ratio I have. Then I can check witch speedo gear I have.
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05-28-2017, 06:29 PM | #7 |
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Re: Speedo gear
The Judging Standards have a chart showing the different speedo gear turtles..Section 4 page 15...revised 2011
I needed a 19 tooth turtle gear for my 3:78 ..I have 21" wheels but the outside diameter may be the same as 19's Also there is this..
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05-28-2017, 06:45 PM | #8 | |
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Re: Speedo gear
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05-28-2017, 06:59 PM | #9 | |
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Re: Speedo gear
Quote:
https://www.fordbarn.com/forum/showt...=177353&page=2
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