Tire size and mileage
#12
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+1 it is a percent off, not actual MPH. So at lower speeds it is less MPH off whereas higher speeds it is more MPH off.
The only way to correct this is to get a tuner or have the dealership flash your PCM, however I wouldn't let a dealership touch it because a "death flash" could be entered. As Sharps stated, a Hypertech or Superchips tuner can acount for gearing or tire size on a Durango so as you put the flash in yourself you enter the information. Then you get the better tune as well as the speedometer fixed.
The only way to correct this is to get a tuner or have the dealership flash your PCM, however I wouldn't let a dealership touch it because a "death flash" could be entered. As Sharps stated, a Hypertech or Superchips tuner can acount for gearing or tire size on a Durango so as you put the flash in yourself you enter the information. Then you get the better tune as well as the speedometer fixed.