Many vehicles require the automatic transmission fluid to be changed when it is warm or hot. However, many experts recommend changing it cold. Most Toyota Corolla cars require the transmission fluid to be changed at least every 20,000 miles (32,187 kilometers) or 24 months, depending on the model and year of the car. Check the owner’s manual to confirm the recommended maintenance schedule.
Remove old transmission fluid, filter and gaskets.
Park the car on a flat surface. You can raise it with ramps or jacks for easier access to the transmission. Make sure the car is securely supported.
Thoroughly clean the outside of the oil pan and surrounding areas to remove all dirt and grease. This prevents contamination when you remove the pan. Remove the dipstick from the filler tube and replace it with a funnel.
Place a drain pan under the fluid pan, remove the drain plug with a socket wrench and allow the old transmission fluid to flow out. If the drain plug has a metal gasket, you can clean it and reuse it. Otherwise, if the gasket is made of fibre, you will have to throw it away and replace it with a new one. Place the drain plug in a place where it won’t get dirty.
Loosen all but two of the fluid retainer pan bolts crisscrosswise. You will need a socket wrench for this step. When only two bolts remain, hold the pan with one hand while you remove the remaining bolts. Be very careful when removing the tray, as it will have some fluid in it. Place the tray on a clean surface.
Remove the filter by removing the screws holding the filter in place. Pay attention if any of these screws are different lengths, so that you can put them back in their correct places. Remove the filter and discard the gasket. You may need to scrape the remaining gasket pieces from the valve body.
Look for the magnets on the bottom of the fluid tray, pull them out and clean them. Don’t be alarmed if you find metal shavings attached to the magnets. The magnets are there to collect this debris so they don’t clog the delicate operation of the transmission.
Empty the rest of the transmission fluid from the pan and wipe the pan with a clean rag. Remove the old gasket. You may have to scrape some of the material off. Wash the pan and drain plug thoroughly and allow them to air dry. Do not dry the pan with a rag, as lint can damage the transmission.
Replace the new filter, gaskets and fluid tray.
Install a new filter unit. Remember to put all screws back in their original places.
Put the magnets back in their original locations. Make sure they do not interfere with the tubing.
Hold the fluid tray and gasket in position and hand tighten the retaining screws in a crisscross pattern. Adjust progressively to 45 to 60 pounds (20 to 27 kilograms) per inch (2.54 centimeters).
Replace the drain plug and gasket by hand. Then tighten with a socket wrench.
Add new transmission fluid
Find the type of transmission fluid to buy that is written on the dipstick. You can also find that information in the owner’s manual. You will probably find that the recommended transmission fluid is Dexron III.
Add the new automatic transmission fluid through the dipstick tube with the engine off. Some fluid will remain in the transmission, so add about half the recommended amount dry to start. Check the level, add the fluid a little more and check again until the fluid reaches the correct level on the dipstick.
Replace the dipstick, start the engine and let it run for a few minutes without pressing the accelerator pedal. Move the gears through the gears and then back to neutral.
Check the fluid level on the dipstick while the car is running. If the dipstick indicates that the transmission requires more fluid, add a little more until the level reaches the full mark on the dipstick.
Tips
Check the drain plug to make sure fluid is not leaking.
Warnings
Do not overfill the transmission with too much fluid. When checking the fluid level, always pay special attention to the hot and cold marks on the dipstick. If the engine is cold, the fluid should be in the “Cold” range on the dipstick. If the engine is hot, the fluid should be in the “Hot” range on the dipstick.