How to Change Transmission Fluid

There's a universal truth about newer cars: They often make do-it-yourself repairs and service jobs more challenging than you'd expect. The same can be true when it comes to changing transmission fluid. First, you have to find the transmission pan, which serves as the reservoir for the automatic transmission fluid (ATF). Because you know the location of the transmission fluid dipstick, you have a good clue. The pan will be sitting directly beneath the dipstick. Unfortunately, some cars require that you remove the oil pan before you can get to the transmission pan. In other cars, you must first remove parts of the exhaust system.

Once you've exposed the pan, it's time to drain the fluid. Some transmission pans come with a drain plug. If you're lucky enough to have such a pan, you can simply remove the plug to drain the ATF. Most transmission pans, however, don't have plugs. The only way to drain the old ATF is to remove the entire pan. Before you do, place a large catch pan under the transmission pan. Then, begin loosening the bolts that attach the pan to the transmission. Be prepared: As soon as you loosen the pan bolts, fluid will leak out around the edges.

Don't remove all of the bolts, as you'll have an overflowing pan of oil and, very likely, a mess. Instead, remove bolts from all but one side, tap the pan with the mallet to break the seal and tilt the pan away from you, letting it pivot on the side with the bolts. The fluid should spill over the lowered side of the pan and into the catch pan. Once the bulk of the fluid has drained, remove the other bolts and the pan. Pour any remaining fluid into the catch pan. Then, to find out how much fluid came out of your transmission, transfer the drained fluid into empty one-gallon milk jugs. You're not looking for an exact measurement -- just a general idea of how much to replace.

Finally, remove the old transmission filter, which is attached to the transmission with bolts, clips or the filter's O-ring seal. You can pull off a seal-attached filter by twisting and pulling on the part. Don't worry about cleaning the filter. It has done its job, and is ready for the trash.

The transmission pan, however, will need some cleaning before you add new ATF. That's the topic of the next section.