Hopefully you have the plastic driving gear on the differential body, inside the transmission case. If you do not see an off-white plastic gear when you look in the fill plug/speedometer sensor unit cavity, it doesn't matter if you have a gear on the end of the fill plug/sensor or not. You won't have anything driving the sensor. A lot of the 1.9L Gen II transaxles have been rebuilt without that plastic drive gear. All the Gen III transaxles being built now probably have the 3.85 ring and pinion as well as the plastic driving gear. Just a "heads up".