In a message dated 8/10/2005 7:23:42 PM Central Standard Time,
sportsix63@yahoo.com writes:
> Are there different speedometer heads for cars with
> and without overdrive?
>
> If they do differ, how do you tell an overdrive
> speedometer from a non-overdrive?
>
The addition of the overdrive did not necessitate any change in speedometers.
After all, the speedometer measures the driveshaft speed. However, tire
diameter and differential gearing do effect the speedometer requirements.
Also, there was a change somewhere in the 74 time frame where they started
changing the speedometer drive gears in the transmission to attain a 1000
turns/mile standard which meant the same speedometer would work in all
applications.
But before this change speedometers were calibrated to work with certain
differential/tire combinations. But overdrive had no effect.
Dave
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