Chrysler Repair: plymouth grand voyageur 3.3:speedo/odo inaccurate?, grand voyageur, calibration factor

Question
will like to know why my speedometer is 10 km off got the rite size of tire

Answer
Hi Roger,
I can't explain what is wrong...do you mean the odometer doesn't read the distance correctly, or that the speedometer doesn't read the speed correctly? or both? If it is a conventional analog type speedometer readout then that could be just a matter of a mechanical adjustment but it would mean taking out the speedometer and opening it up. If the mileage reading is similarly inaccurate as the speed reading, then you could correct both by having the electrical 'pinion factor' in the transmission control module altered using a Chrysler Diagnostic readout box to change the way it converts the pulsing of the output speed sensor to mean a faster/slower and similar further/shorter distance traveled. The pinion factor will change both in the same direction that you choose, but it cannot change only the speed reading without also changing the distance traveled calibration factor. A dealer can do that pinion factor correction, but you would want to measure how far 'off value' the readings are using a measured milepost section on the highway.
Roland