The T56 (stock sendor) has a 17 pulse per driveshaft revolution VSS signal generator incorporated into it. This has to get converted to a 2000 or 4000 pulse per mile signal for your VSS input to the Speedo (likely). There is a conversion box from Dakota Digital that does signal recalibration that converts it to match your speedo. It will also let you know via the LED's if you are getting a signal from the T56. Hope this helps...