Transmissions need a service every two years or 40,000km, whichever comes first. There are many different types of automatic transmissions and many different transmission oils you can buy. It is crucial to use transmission oil that is correct for your car and approved by the manufacturer.
It is common to drain out half of the old oil and top it up with new oil. This provides a very low-quality solution as the dirt stays inside the transmission and the old oil lowers the quality of the new oil.
A better way to service your transmission is with an innovative tool called Geartronic from Germany. Geartronic will clean and pump out all old oil and dirt deposits before filling in the new oil. Geartronic is available at MyCarRepair (T: 076-600069) opposite Thai Watsadu at the Heroines Monument.