Transmission Fluid change & replacement made easy

What does an automatic transmission do?

Automatic transmission is a type of vehicle gearbox that automatically changes the gears whilst in motion. These gearboxes are not the same as Semi Automatic versions, which are in fact a manual gearbox that is automatically controlled.

How does an automatic transmission work and what are the components?

The most common form of automatic transmission is hydraulically operated with a torque converter and a gearset.

The torque converter is a fluid coupling, connecting the engine to the gearbox. In essence this replaces the function of the clutch as it connects and disconnects the engine power to the gears allowing the vehicle to come to a standstill without stalling the engine.

The gearset is a group of planetary gears that provide the required gear ratios and thereby alter the speed of the output.

Automatic transmissions use a special fluid, Automatic Transmission Fluid or ATF for short. This fluid is pressurised by a pump to control the various clutches and bands. An electronic speed sensor controls the pressure produced.

On modern automatic transmissions, the valves are controlled by solenoids actuated by the transmission Control Unit (TCM).

ATF provides the lubrication to the moving parts, wear and corrosion protection and is there to transfer the mechanical power. This is why regular servicing of an automatic transmission is vital to change this fluid (and its filter where fitted) in line with manufacturers recommendation. Failure to do this can result in many issues, such as transmission overheat, solenoid failure, jerky gear changes and even total gearbox failure.

How do you know your automatic transmission needs a service?

If a gearbox hasn’t had its scheduled service, the likelihood is that you will experience some of the following indicators

• Failure to select gears
• Failure to change up and down smoothly (or in some cases, not at all)
• Jerks on gear changes
• Jolts as you change from Park to Drive
• Transmission overheat warnings
• Transmission Control Unit warning lights

How common is an automatic transmission service?

Every vehicle with an automatic gearbox will have a service schedule, the same as the engine does. So this should be a regular occurrence in accordance with this, however in reality, few owners have it carried out until there is an issue, which in some cases it is too late and damage has been done.

How can I extend the life of my automatic transmission?

Quite simply by adhering to the manufacturer's recommended service schedule.

What happens during an automatic transmission service?

There are many different processes required depending on the manufacturer, some of which may include all the following or just some

• Mechanic will raise the vehicle and get the gearbox up to temperature if required by the procedures.
• The gearbox drain plug will be removed, or a syphon pump inserted down the filler tube.
• If the vehicle has a filter, the sump is likely to be removed so the filter can be accessed.
• The parts will then be cleaned before a new filter is installed and the sump refitted with a new gasket or sealing compound.
• The gearbox will then be refilled with the correct ATF for the gearbox and application in accordance with the manufacturer's procedure.
• In some cases the refilling operation requires diagnostic input as well as manual.
• One refilled to the correct level and run through its selection routine, the vehicle will be test driven before returning it to the owner.

How much does an automatic transmission service cost?

The cost of an automatic transmission service depends on your car and what parts the manufacturer recommends for the work. Find out what you could save by having your automatic transmission service carried out by ClickMechanic, by selecting your vehicle at the top of the page