Quand faut-il changer le liquide de transmission ?

When do you need to change your transmission fluid?

Transmission fluid deteriorates over time. In order to prevent damage to the transmission, you should change it frequently enough. How often you should change your transmission fluid depends on how heavy the transmission is used. If you mainly drive in the city, it means that you frequently stop and go. This will increase the operating temperature of the transmission, which means that the pressure is higher on the transmission fluid. Other circumstances such as carrying a heavy load in cars with a high torque or towing a trailer will increase this pressure as well. This heavy use will accelerate the deterioration of the transmission fluid. Overall a change is advised every 90.000 km but this differs per car so always check your owners´ manual to see what range is advised.

How to see whether your transmission fluid needs a change

If you want to check if your transmission fluid is still in a good condition, you can check this on a few factors:

• The first is by checking the color. Transmission fluid is often a light red color. When it starts deteriorating, it will become darker as the fluid gets more burned. This means that the fluid needs a change.
• Transmission fluid should have a sweet smell, it has this distinct petroleum smell. When it smells bad or smells like it is burned, the fluid is definitely is for a change.
• When you drive an automatic and you notice a difference in driving behavior such as transmission slips, rough and noisy shifting, and a lack of drive engagement you should check the fluid.
• The consistency should be smooth, if it has debris or any other particles, it should be changed.

Flushing out vs draining old transmission fluid

When you have decided you transmission fluid is ready for a change, you have two options to choose from on how to do this. The first one is by flushing out the old fluid. This is done by pumping in new fluid and thereby forcing out the old fluid. The advantage of flushing is that flushes out all the debris and metal shavings that was gathered by the fluid. However, if your old transmission fluid is dark and burnt, it is better to drain it instead of flushing. This because flushing could cause the burnt fluid to get the valve body clogged up.

When you want to change your transmission fluid by draining, the pan will be drained and the filter replaced. Not all the fluid gets removed with this method because about 50% of the fluid will stay in the system. Some mechanics drain and fill a couple of times to minimize the leftovers in the system.

Again, always check the owners´ manual to see whether the manufacturer advises flushing or draining.