speedo gear ?
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Logistics Pro
Joined: Jan 2011
Posts: 4,762
Likes: 54
From: Antelope Valley ,CA
speedo gear ?
my 68 speedometer is way off , i have 275/60/15 tires on there any one know what tooth gear i need or the calculation to figure it out ?
speedo says 40mph when i am driving with traffic at 60mph
thanks
in advance
mike
speedo says 40mph when i am driving with traffic at 60mph
thanks
in advance
mike
Last edited by MIKES 68 F100; May 6, 2011 at 05:22 PM. Reason: typo
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Mike, I would suggest that you get under the truck, go with a 3/8" wrench and pull the speedo gear as an early thing to do. Count the number of teeth on the gear. A single tooth +/- is good for about 5 mph. Your's seem very mis-matched.
If you can get on a level garage floor, mark the lr tire at floor contact, hand rotate the tire one rev. while counting the revs of the drive shaft. That will give you absolute ratio, to help work this out.
When I used to go yarding I picked up gears still hanging or laying near a tranny pull. New ones are still available or maybe you can get a used one.
John
If you can get on a level garage floor, mark the lr tire at floor contact, hand rotate the tire one rev. while counting the revs of the drive shaft. That will give you absolute ratio, to help work this out.
When I used to go yarding I picked up gears still hanging or laying near a tranny pull. New ones are still available or maybe you can get a used one.
John
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Logistics Pro
Joined: Jan 2011
Posts: 4,762
Likes: 54
From: Antelope Valley ,CA
found this thanks to google
New Teeth = (Current Teeth x Speedo Reading)/Actual Speed.
Ford Motorsports Also Uses This Formula:
Driven Gear Teeth = (Drive Gear Teeth x Axle Ratio x Tire Rev. Per Mile) / 1000.
so guess i have to pull old one to count teeth , i'll use my garmin gps for actual speed
New Teeth = (Current Teeth x Speedo Reading)/Actual Speed.
Ford Motorsports Also Uses This Formula:
Driven Gear Teeth = (Drive Gear Teeth x Axle Ratio x Tire Rev. Per Mile) / 1000.
so guess i have to pull old one to count teeth , i'll use my garmin gps for actual speed
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 787
From: Simi Valley, CA
Ford has used the same nylon speedometer DRIVEN (end of cable) gears since 1960, 16-21 teeth are available, the prices range from 2 to 4 bucks each.
Speedo DRIVE (on the output shaft of the trans) & DRIVEN gears are determined by the axle ratio, trans type and size of the tires.
Speedo DRIVE (on the output shaft of the trans) & DRIVEN gears are determined by the axle ratio, trans type and size of the tires.
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