the speedo is electric, so replacing the gears won't help. the gears are to fix the odometer only, because the speedo turns the odo as it operates. you PROBABLY need the speedo sender in the rear end. it might also be the connector on the sender. otherwise it's the speedo itself or a voltage problem in the dash. it could be you have a dead odo, also. we won't know that until the speedo works. fyi-to keep from killing the odometer, do not push the reset button for the trip odo while in motion. the numbers roll backwards when resetting and so the car has to be still, unless you are LITERALLY backing up the car. good luck, chuck.