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Old 06-16-2020, 04:59 AM   #1
Gino
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Default 65 Falcon speedometer

Hi. When Iím traveling at say 50 mph my speedometer is reading 60 mph. Iím told there is a gear in the Trang that is somewhat easy to replace, but how do I know what gear I need? Thanks
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Old 06-16-2020, 06:03 AM   #2
Dobie Gillis
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Default Re: 65 Falcon speedometer

You need to know what axle ratio you have. Are your wheels/tires stock size or close to it?
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Old 06-16-2020, 09:35 AM   #3
51504bat
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Default Re: 65 Falcon speedometer

When I was in HS I changed my '65 Falcon from an auto to a stick along with the third member. I changed the gear on the end of the speedometer cable that inserts into the trans to make the speedo read more correctly. They come in different tooth count depending on the application. The photo is just an example. But I also had bigger tires so it was never spot on. What I should have done was go to a speedo shop and have them calibrate the speedo using an adapter like the one pictured.
Attached Images
File Type: jpg speedo gear.jpg (14.9 KB, 0 views)
File Type: jpg SpeedoReduction.jpg (49.2 KB, 0 views)
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Old 06-16-2020, 10:32 AM   #4
Dobie Gillis
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Default Re: 65 Falcon speedometer

Speedometers have a built-in fudge factor and will read a few mph faster than actual speed. My daily driver, a Kia Optima, Reads 2 mph faster than actual with stock wheels & tires. My '55 Merc reads about 5 mph faster than actual. I measure actual speed with a GPS speedometer app on my cell phone.
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Old 06-17-2020, 10:30 AM   #5
Gino
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Default Re: 65 Falcon speedometer

ok, well im not looking for it to be exact, so would you say more teeth or less teeth mould bring me in closer? thanks again
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Old 06-17-2020, 11:02 AM   #6
dmsfrr
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Default Re: 65 Falcon speedometer

More teeth on the gear at the lower end of the speedo cable will cause the speedometer to read lower.
It's been too many yrs since I did one but the change may be 5% per tooth, if memory serves...

FYI - if you have mile markers on a hiway near you double check the odometer readings against the mile markers before changing things. It's possible for the odometer to be correct and the speedometer to be off.
If the odometer is correct so is the gear on the cable, but the speedometer itself needs attention.

<<< This red car is like that. The odometer is dead-on but the speedo reads high.
(it's possible because the odometer is gear driven but the speedometer works on spinning magnets)
.

Last edited by dmsfrr; 06-17-2020 at 12:06 PM.
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Old 06-17-2020, 05:41 PM   #7
rotorwrench
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Default Re: 65 Falcon speedometer

The parts books used to have a chart but it depends on what book you have in the later years. They would factor tire size and axle ratio. Those little ratio adapters are available so a person can get a cable drive as close as possible. There are charts for them too. A person also needs to know the speedometer ratio as well.
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