Back to what I was trying to explain yesterday. Most tires have a spec for how many revolutions make a mile. If not you can calculate the circumference from the diameter then divide 5,280 by the circumference to figure out how many revolutions they turn for a mile. The revolutions per mile needs to be multiplied by the rear gear ratio to get the number of transmission output shaft rotations per mile. That value needs to be loaded into the Trans/Revolution per mile constant. Then that value needs to be multiplied by 40 to get the number of VSS pulses per mile. The VSS reluctor is on the output shaft of the transmission and has 40 teeth. Once that is done the speedo should be close. If it is off a little can play with the VSS pulses per mile to fix it. Finally your ABS pulses per mile need to be rescaled by the same ratio you used for the trans revolution/mile. Take the old number that was stock in the computer and the new value and run them through a percentage difference calculator. Use that percentage to calculate the new abs-mile setting. If you fail to fix the ABS pulses for the new gears the ABS light will frequently illuminate and drive you crazy.
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