Remove the cable terminal from a negative terminal of the battery. If the model comes with a manual transaxle, then safely lift the car and put it on stands, then remove the wire harness from the VSS. Then, take out the VSS from the transaxle after which, the VSS drive gear can be withdrawn together with the old O-ring which has to be disposed off. I leave a new O-ring inside the housing of the VSS before I refit the drive gear as well as the VSS while using the retaining bolt. The process of installation is vice versa to removal process. If the car model has an automatic transaxle, there is the need to remove, in that order, the air filter housing, battery, battery tray and bracket. Remove the input shaft VSS electrical connector and then remove the input shaft VSS from the transaxle and throw the old O-ring before installing the new one then tighten the VSS. Second, disconnect the VSS electrical connector of the output shaft VSS, disconnect the VSS of transaxle, and throw the old O-ring away, and then insert a new O-ring and fasten down VSS tightly.