Most cars on the road today have automatic transmissions and so require automatic transmission fluid, or ATF. The pressure changes within the ATF and causes the transmission to switch gears. Unfortunately, transmission fluid temperature rarely stays in the optimal range due to driving conditions stop / go driving, driving long distances etc this can heat transmission fluid beyond acceptable limits. At these higher temperatures the ATF begins to break down, and your transmission begins to shift gears more roughly, this is why most manufacturers recommend that you change your ATF every 20,000 to 25,000 miles. Changing the transmission fluid in a manual transmission works a little differently, so we recommend you should consult your owner’s manual or, better yet, take your car to a good mechanic.
There is a bewildering array of different ATF types and specifications. Most automatic transmissions can take either Dexron II, Dexron III or DIII MV – ATF Multi Vehicle, but that’s a broad generalisation. For example, most domestic Fords from 1992 or earlier require Type F fluid, which is also used by Toyota. To be safe, again consult your owner’s manual or dealer to make sure you’re using the right replacement fluid.
Inspect your transmission to diagnose its health. Your car will need to be running to do this, so start the engine and let it run until it gets warm. With the gears in park or neutral and the brakes on, check the transmission fluid level using the dipstick located at the rear of the engine. Pull out the dipstick, wipe it on a clean rag and reinsert it into the tube, making sure it’s seated completely. Pull the dipstick out again and look at the film of fluid on the end. Some dipsticks indicate add levels, and some show full levels for cool, warm or hot fluid. If your transmission is in good health, the automatic transmission fluid (ATF) should not be low. It should also have a pinkish to reddish colour and a good smell of petroleum.
If the fluid level is low and you’re in between service, add transmission fluid and keep checking every two weeks. If your transmission fluid is consistently low or appears burned and dirty, you could have a more serious transmission problem. Take your car to a mechanic so the transmission can be thoroughly inspected.
If the fluid level and quality looks good and it’s been 20,000 miles (32,187 kilometers) since your last transmission service, you should proceed with the fluid change.
There are two different approaches to changing automatic transmission fluid (ATF).
1st Involves pumping out the old transmission fluid before adding the new. This approach has the advantage of removing more of the old fluid, even the ATF that collects in the nooks and crannies of the torque converter, but it’s a bit more complicated.
2ND Is called known as the “drop pan” method, doesn’t require any pumping. As a result, it’s much easier to do, although it leaves behind some of the old fluid to mix with the new ATF you add.
So to help you with the Drop Pan method you will require:
- Socket wrenches
- Longneck funnel
- Two old milk containers
- Jack stands or car ramp
- Wheel chocks or block
- Brake cleaner
- Several clean shop rags
You’ll use the milk jugs for measuring, not collecting. You can get by without them, but it’s handy to know how much fluid gravity pulls from your transmission. When you go to add new ATF, you’ll have a ballpark idea of how much fluid to add.
Before you start if your transmission fluid is consistently low or appears burned and dirty, you could have a more serious transmission problem. Take your car to a mechanic so the transmission can be thoroughly inspected.
If the fluid level and quality looks good and it’s been 20,000 miles since your last transmission service, you should proceed with the fluid change. To do this, you’ll need to raise your car. You can use jack stands, but ramps make the job easier, but either way jack stands or ramp it’s best to have wheel chocks ready to keep the rear tires from rolling.
Transmission Fluid changes should only be done when the engine and transmission are at normal operating temperatures. With your vehicle raised, let the engine idle for a few minutes, then turn it off. When the transmission fluid is still warm, but the vehicle has cooled down, you’re ready to remove the old transmission fluid.
There’s a universal truth about newer cars: They often make DIY 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 as the pan will probably 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 slowly that are attach the pan to the transmission. Be fully aware that as soon as you loosen the pan bolts, fluid will start to leak out around the edges.
Do not 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 the empty milk containers. You’re not looking for an exact measurement, just a general idea of how much to transmission fluid you need 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 the 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 bin and need replacing with a new filter.
However, the transmission pan will need some cleaning before you add new ATF. Use a rag to wipe away the residue from the inside of the pan. Don’t be alarmed if you find metal debris, even healthy transmissions will leave small amounts of metal in the pan. Next, remove any traces of the gasket from the edges of the pan. You should be able to peel away most of the gasket by hand, but some sticky residue may remain. Use a knife or flat-head screwdriver to scrape off this residue, being careful not to scratch the surface of the pan. Brake cleaner will remove any stubborn bits of gasket material. You can also apply brake cleaner to the pan bolts.
While the pan and pan bolts dry, install the new filter. Make sure it’s mounted in the same position and that the O-ring is properly positioned. Reattach any bolts or clips that secured the filter to the transmission. Then you can reinstall the pan, using the gasket either rubber or cork as recommended by the manufacturer. Many rubber gaskets are self-sealing, but some rubber gaskets and most cork gaskets are not. If your gasket is of the latter variety, apply the recommended fastening cement or glue before you install the gasket. Start every pan bolt by hand for a couple of turns or so before tightening. You don’t want to over tighten the bolts, as this will flatten the gasket and cause leaking. If no recommended torque is given, make the pan bolts “screwdriver tight.”
Now you’re finally ready to add new transmission fluid. Most vehicles allow you to do this through the dipstick tube, using a longneck funnel. Pour a little less than the amount of automatic transmission fluid (ATF) you collected in the milk containers. Next, start the engine and let it run idle for at least one minute. With the parking and service brakes applied, move the gear stick through each position, ending in park / neutral. Recheck the fluid level and add fluid to bring the level to an eighth-inch below the add mark. Run the engine until it reaches normal operating temperature, and then recheck the fluid level, it should be in the hot region.
A word of caution about adding ATF: Overfilling can be just as bad as having too little fluid. So go slowly, check the dipstick often, and in no time you’ll be back on the road with a happy and healthy transmission.