Speedometer gear question
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Speedometer gear question
I have just been given a 1978 F150 Custom that belonged to my Grandfather, then my Father. It has a 302, with the 4 speed manual floor shift(3 with o/d), 3.00 gears in rear end, and will be putting 225/75/15 inch tires. The speedometer gear is not present at all. Does anyone have any idea what gear to put in this truck? It is definitely all stock.
Mike
Mike
Fleet Mechanic
Joined: Feb 2007
Posts: 1,326
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From: Middle TN
Ford Motorsports Uses This Formula:
Driven Gear Teeth = (Drive Gear Teeth x Axle Ratio x Tire Rev. Per Mile) / 10
225/75/15 = 735.5 tire revolutions per mile.
You need to count the number of teeth on the drive gear (in the transmission).
These are hard to count. Clean the oil off a tooth and mark it with a sharpie, then count.
Driven Gear Teeth = (Drive Gear Teeth x Axle Ratio x Tire Rev. Per Mile) / 10
225/75/15 = 735.5 tire revolutions per mile.
You need to count the number of teeth on the drive gear (in the transmission).
These are hard to count. Clean the oil off a tooth and mark it with a sharpie, then count.
