Thread: Ford speedo gears
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10-26-2018 10:22 PM #1
Ford speedo gears
I need a gear with one more tooth and it should be right on,I have a 21 tooth gear and would like to find a 22 and anyone have any parts manuals. The parts guy at the dealer I was at the other day did not have a way to look up old part numbers,
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10-27-2018 04:02 AM #2
Did you try looking on EBay? A lot of sellers there list the gears according to tooth count.Steve
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10-27-2018 05:06 AM #3
Also, it’s easy to mathematicaly calculate a gear change, so you don’t have to guess which gear to buy.
How far is your speedo off, and what speed did you check it at?
Adding one tooth to a 21 tooth gear, (1 divided by 21) will slow down the speedometer by 4.7%
60 MPH minus 4.7% equals 57 MPH. (0.047x60 equals 2.82 MPH change)Steve
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10-27-2018 06:45 AM #4
Its about 2 too fast and can not remember the speed it was checked.
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10-27-2018 09:51 AM #5
A local transmission shop is often another good source for gears.
.I've NEVER seen a car come from the factory that couldn't be improved.....
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10-27-2018 01:21 PM #6
Found none on ebay,plenty of 21 and 23 tooth gears but no 22 so I am going to leave it alone. I want to get it as close as I can to check gas mileage.
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10-27-2018 02:18 PM #7
Assuming you are using a stock 55 Ford transmission CLICK HERE
Suggested speed to clock your speedometer would be 60mph. Believe it or not, the local police will help you do so if you ask.Last edited by mrmustang; 10-27-2018 at 02:20 PM.
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10-27-2018 02:48 PM #8
Late 70s C-4
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10-27-2018 03:08 PM #9
In that case, Ford, and the aftermarket do not offer a 23 tooth speedometer gear
These are your options for the C4 automatic transmission.
19 tooth-tan
20 tooth-orange
21 tooth-red
23 tooth-white
At this point, you are going to have to deal with tire size changes (small, simple, yet can be costly).
Another option is to find a measured mile (a real one, not what you see marked on the side of a typical road), take measurements, then send the speedometer itself out for re-calibration to match what you need it to be.
Looking back, you did not make mention of whether you are using an original or aftermarket speedometer. Which are you using, be as detailed as you can be, include tire sizes (rear only), rear gear ratio, type of rear end, speedometer head, any adapters, etc.
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10-27-2018 03:33 PM #10
Its almost a tenth of a mile too fast according to the mile markers.
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10-27-2018 04:48 PM #11
Get a GPS and it will tell you your MPH then look at your speedometerCharlie
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10-28-2018 07:02 PM #12
Here is a possible solution;
Ratio Adapter
https://www.bobsspeedometer.com/1/120/ratio_adapter.aspSteve
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