Speedometer gear tables
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5th Wheeling
Joined: Jul 2024
Posts: 47
Likes: 5
From: Central NY
Speedometer gear tables
I am replacing my speed sensor. I am planning on replacing the driven gear while I am at it. I have been searching for any indication of the proper driven gear, but I am unable to find it. I saw the tables posted online at garysgaragemahal, but it doesn't list my combination. does anyone have the tables for 1989 they could share?
Also, I bought the digital shop manuals package from Rock Auto, but despite my inquiring, they DO NOT have parts diagrams or part numbers. Frustrating. I guess I'll buy the other digital manuals that (presumably?) have all part numbers...
Also, I bought the digital shop manuals package from Rock Auto, but despite my inquiring, they DO NOT have parts diagrams or part numbers. Frustrating. I guess I'll buy the other digital manuals that (presumably?) have all part numbers...
i ain't rite
Joined: Mar 2005
Posts: 65,448
Likes: 5,518
From: Marlboro Mental Hospital.
red is 21 tooth, black is 20 tooth, natural is 19 tooth, yellow is 18 tooth, 17 tooth is white, wine/burgandy is 16 tooth
one tooth equals about a 1.5 mph difference.
more teeth, slower speedometer reads. less teeth higher it will read.
one tooth equals about a 1.5 mph difference.
more teeth, slower speedometer reads. less teeth higher it will read.
Cargo Master
Joined: Aug 2021
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From: Maryland
Cargo Master
Joined: Aug 2021
Posts: 2,251
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From: Maryland
Hotshot
Joined: Jun 2015
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Hotshot
Joined: Jul 2020
Posts: 10,354
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From: Near Salt Lake City
We never used a table to figure the speedometers out
You go 60 miles per hour on the gauge and measure the distance traveled at the same time using the mile markers on the freeway
1 tooth equals 5 miles an hour at 60
You are talking about driven gears and they make different drive gears too
You need a Ford parts department catalog, that uses your rear axle ratio and tire size, to come up with what the stock color was
Simply figure out how far off you are, (how many seconds) off at 60 miles an hour on the freeway
You go 60 miles per hour on the gauge and measure the distance traveled at the same time using the mile markers on the freeway
1 tooth equals 5 miles an hour at 60
You are talking about driven gears and they make different drive gears too
You need a Ford parts department catalog, that uses your rear axle ratio and tire size, to come up with what the stock color was
Simply figure out how far off you are, (how many seconds) off at 60 miles an hour on the freeway
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Hotshot
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Hotshot
Joined: Jun 2015
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Do you not understand how to use the formula? Tire manufacturers list the revolutions per mile for their tires or at least they used to which is how I figured out what driven gear I needed for the FSB when I went from the original 215 or 235 tires to 35” tires
Seriously? How many people have access to the old microfiche and a viewer.
Seriously? How many people have access to the old microfiche and a viewer.
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5th Wheeling
Joined: Jul 2024
Posts: 47
Likes: 5
From: Central NY
The whole point was to have a new gear purchased and ready, prior to assembly. Obviously, then, counting teeth doesn't work. None of that other stuff helps, either.
Anyway, it was 19 teeth.
Anyway, it was 19 teeth.
Laughing Gas
Joined: Jul 2009
Posts: 1,000
Likes: 402
From: NE Ohio
Some transmissions have the drive gear as part of the output shaft., 7 or 8 tooth being the most common. That makes that difficult to change - you'd need to take the trans completely apart to change the output shaft. After that, you need to calculate your tire revs/mile (which changes with tire diameter). Only then can you try to figure out which driven gear will get the closest to being true. My AOD had the wrong output shaft tooth count when I went from 2.75 to 3.55s. I had to use the 22-tooth driven gear, which tends to wear/fail early. If I would have had the other drive gear shaft (yes, it is part of the shaft on AODs.), I could have used a more common and less failure-prone driven gear.
IIRC, C-6 drive gears are replaceable, held to the output shaft by a spring clip. It has been 30 years since I played with a C-6, so I could be wrong... .
IIRC, C-6 drive gears are replaceable, held to the output shaft by a spring clip. It has been 30 years since I played with a C-6, so I could be wrong... .
Hotshot
Joined: Jun 2015
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Then you can use that information and the formula in the chart to calculate what new gear you need.
I didn’t have to change the drive gear on my C6. Only the driven gear and that has almost been 30 years since I did that.
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