Automatic transmission needs little maintenance other than regular checking of the transmission fluid level.
Most failures are caused by a level drop through evaporation or leakage (see checking the transmission fluid level, drain and injection), or because the engine is idling at such a speed that is incorrect when you check the level.
Check in the car handbook which particular fluid should be used for your car. Topping up with the wrong fluid can damage the transmission. (In some smaller automatic gearboxes, such as those used in BL cars, the transmission fluid is the same oil as that which lubricates the engine, and is drawn from a common sump.)
Keep the liquid out of the test paper. Do not install too much may lead to overheating.
The sump and the ventilating grilles on the torque-converter housing can easily become blocked or mud covered, and this leads to overheating. Check and clean them at each service.
Checking the fluid level
The transmission fluid level is best checked when the engine is at normal running temperature. After a 5 mile run, park on level ground and apply the handbrake.
With the engine idling, move the gear selector lever at least three times through all positions. Set it in the ‘P’ (park) position and let the engine idle for two minutes.
Before removing the dipstick, wipe round it with a clean cloth to stop dirt entering the gearbox.
With the engine idling, remove the test paper, wipe clean, no fluff cloth. Gently replace it so that it does not force the fluid back up the ruler so give a false reading. Immediately withdraw it and check the level.
Check the fluid on the dipstick for specks of dirt or metal — both indicate wear. If there are any, get expert advice as soon as possible, before the repair becomes very expensive.
Especially in old cars, check the color of the liquid against the color of the new liquid. If a red liquid darkens or darkens, it indicates that the economy is overheated and the liquid should be changed.
Topping up, draining and refilling automatic transmission fluid
Top up the fluid levels through the dipstick tube, using a small funnel. Add a little at a time and check the level frequently to avoid overfilling.
The difference between the low and full marks on most transmission dipsticks is about 1/2 litre (about 1 pint). So if the reading is midway between them, about litre pint) is needed.
If you have the highest liquid level, and the engine is cold, fill 1/2. (13 mm) below the test strip. Otherwise it will overheat at normal operating temperatures, which can cause overheating.
Check the level again at normal running temperature.
Some car handbooks recommend draining and refilling automatic gearboxes at certain fixed mileages.
However, most automatics fitted to recent and current cars do not need regular draining, and do not have a drain plug.
Drainage is a very difficult and trivial task that requires removal of the foot tube and gearbox oil pan, the task requires cleanliness of the working conditions and garage facilities. Follow the manufacturer’s recommendations in the car manual or service manual.
The smaller automatic gearboxes do have drain plugs, and the fluid must be changed at the intervals recommended in the car handbook.
Those fitted to BL cars, which use the same oil as the engine, receive fresh oil when the engine oil is changed. Others, such as those fitted to some VWs and Renaults, have their own separate fluid supply.
The transmission should be drained while the fluid is at normal running temperature. Take care: it will be hot enough to cause serious burns.
In most cases, draining must be done with the car raised and supported securely on axle stands or ramps and with the handbrake on.
Place the drain tray under the sump, and undo the plug, keeping your hands and arms clear of the hot oil when it gushes out.
When all the oil has dried up, replace the drain plug and add the recommended liquid or oil type manual or service manual.
Refill with the quantity recommended, and drive the car until the new fluid is at normal operating temperature, then check the level again and top up if necessary.
It is important not to waste the old liquid and pollute the water. Ask your local commission to locate the nearest oil handling dump and take it there.
How to avoid overheating
How to tow an automatic car
Cars fitted with modern automatic gearboxes must not be towed for a distance of more than about 15 miles. The towing speed must also be kept under 30 mph (50 kph).
The reason for these limitations is that the internal fluid pump gearbox, driven by the engine, does not work when the engine is not running.
When the car is being towed, therefore, the box is not lubricated or cooled.
If the car is trailing more than 15 miles – in the event of a malfunction, for example, raise the drive shaft to drive the wheel or disconnect or drive the shaft.
If the car is towed by a garage or fault recovery service, make sure they know the car’s automatic transmission, but they do not drag too big or too fast.