Replacing your car's automatic transmission fluid can save you time and money that you may otherwise incur by taking your car to a professional mechanic. While most automotive professionals would consider the procedure a relatively simple one, it is important that you follow similar techniques to achieve a successful transmission fluid replacement and keep your car running well.
Put on protective eyewear and gloves. Transmission fluid can damage the eyes and irritate the skin if direct contact is made, so take the proper protective caution before beginning.
Open your car's hood and remove the transmission fluid dipstick. According to Popular Mechanics, your car's transmission fluid should be bright red in color and should smell like petroleum. If the transmission fluid is brown or black, and if the levels are very low and hard to see, the transmission fluid needs to be changed.
Engage your car's emergency break. You want to make sure that your car does not move while you are underneath it.
Disconnect the transmission's cooling line with a wrench. The cooling line is connected to the car's radiator. If you are unsure what the cooling line looks like, refer to your car's manual or consult the drawing at Reference 1.
Insert a piece of rubber tubing into the cooling line and allow the other end to drop down into a large jug (a milk jug would work well here).
Start your car. When the car is started, the transmission fluid should leave the cooling line and run into the jug. When the transmission fluid has stopped flowing, turn your car off and reconnect the cooling line to the radiator.
Remove the drain pan. The drain pan was what was connected to the cooling line and what the transmission fluid was flowing out of. Depending on the type of transmission drain pan you have, you may have to remove one or two bolts at either end with a wrench. Be careful when you do this, as there could be some remaining transmission fluid inside the drain pan, in addition to dirt and debris.
Wash the drain pan thoroughly with warm water. Make sure to remove all remaining transmission fluid, sludge and dirt.
Replace the transmission filter, which is located inside the drain pan. If the transmission filter is secured to the transmission, you will have to remove the bolts to remove it completely. It is possible to purchase a transmission fluid kit at most automotive shops. Many times, these kits come with replacement filters and seals. Do not try to simply clean the filter and reuse it. If you are unsure of which filter to buy for your car, consult your car's manual or ask a mechanic. The replacement filter needs to be exactly the same as the old filter.
Reattach the drain pan to the transmission with a wrench. Do not overtighten the bolts, as these could strip the bolts and cause damage to the pan.
Refill the transmission fluid with a generic automatic transmission fluid, such as Dextron. Your car's manual should specify a type of transmission fluid that should be used with your automobile. If in doubt, you can always consult with a local mechanic for a recommended brand.
Dispose of the old transmission fluid at a local recycling center.
