Speedo gears

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lilhows340

lilhows340

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Hi does anyone know if the gears selection changes between 100 mph speedo over a 120mph speedo. My speedo reads 25% high. I have the 120 mph. I also have an a230 3spd numbers matching to 72 Demon340. Haven't been able to find a chart specific to a230's
 
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Speedo gears should be the same. Something changed like tire size or calibration of Speedo cluster.
 
The speedo gears fit all trans types, 1966 to late 70's.

The difference is inside the speedo.
 
Syleng1 said:
Something changed like tire size or calibration of Speedo
Click to expand...

lilhows340 said:
My speedo reads 25% high
Click to expand...
So it sounds like you changed from a 100 mph to a 120 mph speedo.

Was the 100 speedo accurate?

If so the 120 speedo may need to be internally calibrated.

You can verify this by driving a known distance. The longer the better! Recording the odometer at start and stop. If the miles are very close to accurate (ie not 25% off) then the speedo gear is correct for you rear gear ratio and the tire height.

If on the other hand the miles are off by 25% then the 100 speedo was out of calibration and the 120 is more accurate. Change the speedo gear to correct the miles to be accurate and THEN if the Speedo is off have the Speedo calibrated. Or live with it.
 
Measure your rear tire height, and choose which rearend gear ratio you have. Where those lines intersect in the chart below is the speedometer gear you need in the transmission...no matter what transmission it is. Also, you have to set the speedo gear adapter into the transmission for the specific speedo gear you chose.
www.forabodiesonly.com

Speedometer Gear Charts - Clarification/Differences

I recently changed my speedometer gear due to a rear end change. I found the following information out while deciding what speedometer gear I needed. Almost all sites point to an axle ratio to tire size chart that lists the corresponding teeth count such as below; I queried tiresize.com and...
www.forabodiesonly.com www.forabodiesonly.com
 
take out the current gear and count the teeth (may be printed in little circles on the flat of the plastic gear). Buy a gear with 25% more teeth...
 
I did all the calculations for the gear tire size exc. and it came up with a 36 tooth. I did a full restore on this car. Rebuilt dash cluster and and reset odometer to 0. Before I order a gear I'm going to check distance as Dana suggested. May have mixed parts from 100 and 120 mph speedos duh.
 
I switched from a 150 speed-O to a 120, just to get the better graduations. I used the same transmission Speed-O gear.
However, I have seen cables be a problem in the transmission of the "signal".
 
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