Order of execution
1. Disconnect the drive shaft from the gearbox.
2. Use a flathead screwdriver to remove the O-ring from the gearbox housing.
Warning! Clean the O-ring seat and apply a thin coat of oil to it
3. Using Drift 09431-21200, install a new O-ring into the transmission case seat.
4. Lubricate the sealing lip of the new O-ring with oil.