Why It’s Never Good Enough to Simply Replace the Fluid in Your Automatic Transmission

Most people know how important it is to change their engine oil and filter whenever told by the manufacturer. They book their car in for a service, and it'll be taken care of by their trusty mechanic. Yet, did you know that you should also schedule an automatic transmission service from time to time and that there is more to this than meets the eye? What should you pay attention to?

Inside the Gearbox

An automatic transmission is a marvellous feat of engineering. You, as the driver, do not need to change gears or worry about that biting clutch as the magic within the gearbox will take care of it all. And a lot is going on within the gearbox casing, especially when it comes to a critical component known as the torque converter.


The torque converter uses hydraulic pressure to match the engine's speed with the gearbox and select the appropriate gears for the occasion. There is a centrifuge inside which spins at an incredible speed, and as it does so, it throws transmission fluid outward towards the wall of the casing. As this takes place at such a high velocity, tiny imperfections or specks of dirt will stick to the wall of the case and, over time, will build up. If you do not do something to eliminate this accumulation, big problems could be on the horizon.

Danger Ahead

When that accumulation reaches a certain point, there is a risk that parts of it will break free and find their way into the sensitive mechanical components. They could cause unwanted friction and failure if you are unlucky.

The Proper Approach

This is why it is so important to flush the transmission fluid whenever it is replaced. It is simply not good enough to remove the liquid from the transmission pan and change the filter. This work will only get rid of a percentage of the total fluid and, importantly, leave some of the older stuff in the torque converter.

Doing It Properly

When you take your vehicle to a mechanic and specify that you want your automatic transmission to be flushed, they will attach a special machine to your car. It'll get rid of the fluid in its entirety and, importantly, will also clean the inside of the casing wall. The mechanic will then replace it with brand-new fluid and you should be good to go for the foreseeable future.