How to care for your auto transmission

The transmission's filled on the assembly line and will never need servicing. But to take that advice on face value is to court disaster.

The fluid in an automatic transmission is its lifeblood, it depends on it to operate efficiently over a long period of time, and to ignore it is to risk an expensive meltdown.

While carmakers tell you automatic transmissions don't need servicing, specialists in the field say regular maintenance is required to keep them working the way they should.

It doesn't matter what you're told, oil does break down over time, and with high temperature, and its efficiency is reduced.

The service routine recommended by specialists for cars in normal use is to change the oil and filter every 12 months, which equates to 20,000 km, and carry out a full flush of the transmission every two years.

For vehicles working in more punishing conditions, such as hilly terrain, on sandy tracks, using four-wheel in the bush, or towing regularly, those intervals should be reduced.

It's also important to ensure the fluid doesn't overheat, which usually happens because the transmission is worked too hard. If you plan to tow with your vehicle on a regular basis, like on that dream trip of a lifetime around the country, consider having an external transmission oil cooler fitted.

It's also important to select the best gear in which to tow for the conditions.

On the flat it's ok to drive in top gear, which is usually an overdrive gear in modern five or six-speed gearboxes, but it's important to read the road ahead when you do that, and change down one, or perhaps even two gears, when approaching an incline or hill. Leaving it in top gear will force the engine and transmission to work harder when you hit the hill, and the temperature in the transmission will rise as result.

But selecting a lower gear on the approach to the hill will get you up and over the hill without excessively stressing the transmission.