Nope - the speed comes from the rear ABS sensor, which is driven from a tone
ring. Speed is calculated by the computer taking the axle RPMs and
multiplying by a pre-programmed "pinion factor", which equates to the
diameter of the tire.
In short, change the gear ratio all you want - you won't change your
speedometer reading. Change your tire size, and you'll have to re-program
the PCM, or install an electronic device to compensate.
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