change the speedometer constant

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Dec 27, 2014 | 03:07 PM

f150truckguy

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change the speedometer constant

I was wondering if you install bigger tires on a truck, but don't change the speedometer constant can that mess up the transmission due to it all being computerized. I have a 1995 ford f150 that had bigger tires on it than stock when I bought it I realized that the speedometer was off by a few miles from point A to point B so I looked into it and found out how to change the calibration now that I have done that the transmission shifts differently and is a little more responsive is this a true feeling or is it just coincidence.

Dec 27, 2014 | 04:13 PM

rla2005

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The PCM relies on accurate Vehicle Speed feedback to control the transmission. You are experiencing exactly what I would expect after correcting the PSOM constant.