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Old 02-12-2010, 05:35 PM
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Changed Differential, Now How Do I Calibrate the Speedometer? '49 Ford F-1

1949 Ford F-1 truck. I put a Ford 9" rear axle under it with a higher differential ratio, naturally the speedometer is way off.

Still running the stock 3 speed transmission.

I assume I need to change out the gears in the transmission that feed the speedometer. I don't have the machine tools necessary to make my own.

Is there a source for a new gear set, or what would you guys suggest?

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Old 02-12-2010, 05:53 PM
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Quote:
Originally Posted by wavetrain75
1949 Ford F-1 truck. I put a Ford 9" rear axle under it with a higher differential ratio, naturally the speedometer is way off.

I assume I need to change out the gears in the transmission that feed the speedometer. I don't have the machine tools necessary to make my own.

Is there a source for a new gear set, or what would you guys suggest?
Depending on what tranny you're using, you can either change the speedo gears like you mentioned (HERE is the TCI calculator- they also sell the gears), or use an add-on calibration unit that mechanically alters the trans speedo output to correct for tires or gear changes.

The add-on unit attaches like your speedo cable does, to the tranny. Then the speedo cable is attached to the unit.

Sometimes the speedo head can be recalibrated.
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Old 02-13-2010, 06:57 AM
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Quote:
Originally Posted by wavetrain75
1949 Ford F-1 truck.

Is there a source for a new gear set, or what would you guys suggest?


When I needed to changed the speedometer calibration on my 1948 Ford ... I changed this. This bolts on to the transmission and the speedometer cable goes to it. The one in the photo is a 19 tooth A 18 tooth would speed the speedometer up. A 20 tooth would slow it down.

A 1949 Ford F1 may have a different speedometer drive setup. ( I had a 49 F-1 I installed a SBC into many years ago ,,, but it has been too long to remember ) ... but there are companies who sell a speedometer adapter ... geared to fix your problem.



I suggest you read this

http://www.speedometershop.com/ratio.html

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