Chrysler Repair: Electronic cluster reads speed/distance erroneously: 94 electronic trans, chrysler dealer, sf bay area

Question
I have a '94 town and country that has digatal dash problems.  The listing for  milage and speed read wrong , almost double what it should.  For example when driving 35mph it will say that your going 50 something. What is causing this and what do i need to replace.

Answer
Hi Nicole,
If the mileage and speed readings are erroneous in the same direction and by the same factor, then I suspect there is nothing wrong with the cluster itself. Rather I would believe that the "pinion factor" that is programmed into the powertrain/transmission control computers is in error. That factor is adjustable to take into account the gear ratio of the output gear of the transmission and the size of the wheel/tire combination (the circumference of the tire) that are installed on the front of the van. This error may have occured if you had the transmission computer changed or modified your front wheel/tire sizes.
To adjust the pinion factor you need to go to a Chrysler dealer or an independent shop that has a Chrysler Diagnostic Readout Box II (which was superceded by the III model in the latter half of the 90's). I have the instructions on how to use the DRB II to change the pinion factor if you can find a shop with device that doesn't know how to do the adjustment. I live in the SF Bay area of California should you live nearby that let me know. I have a DRB II and could try it myself. I hope this adjustment would be able to correct the error for you.
Another possibility that I just thought of, in fact probably the most likely cause of your problem, is that you have accidentally changed the readout of the cluster to show speed and distance in kilometers rather than in miles. That would cause an error of a higher readings by a factor of about 1.6. So look at the reading and see if they say mph and m, kph and k. If the latter are displayed, than push the button that modifies the readout to drop the reading by a factor of 0.62.
Roland