By Tom Morr
Vehicles' vital fluids normally perform two important functions: lubricating and cleaning. As the fluid circulates through the parts, it gathers the dirt and metal shavings that can accumulate over time. If you're lucky, this debris will settle on the bottom of the pan or housing and not circulate through the system. That’s why some auto shops use machines that perform a transmission fluid flush, ensuring that more of this debris is removed before any new transmission fluid is poured into the vehicle.
Nothing prolongs vehicle life more than regular fluid changes. In automatic transmissions/transaxles, the recommended service interval is about every 30,000 miles or 30 months. (Check your owner's manual or service manual for your car's specifics.) The automatic transmission fluid (ATF) should be changed sooner if its dipstick reveals dark or burnt-smelling fluid.
DIY transmission fluid and filter changes
Even those of us who change our own oil often cringe at the prospect of draining ATF. Because many transmission pans don't have drain plugs, changing the fluid can be a messy proposition –the entire pan must be removed. But even on vehicles that do have drain plugs, the pan still must be removed to change the filter.
Changing transmission fluid is one of those messy jobs that someone has to do. Doing the deed yourself will save money, possibly time and fresh ATF can make your gearbox perform young beyond its years. It’s also relatively easy to determine when your ATF may be low. Consider an automatic transmission service if you detect the following signs of low transmission fluid:
- Transmission slips
- Transmission shifts roughly
- Noisy transmission
- No drive engagement in forward or reverse gears
How to change automatic transmission fluid: Step-by-step instructions
If you can garner some initial patience, learning how to change automatic transmission fluid will only benefit you in the long run. More importantly, you’ll need an automatic transmission filter kit; they normally contain a gasket for the pan in addition to the new transmission filter and its O-ring. Along with some basic shop tools, you’re ready to get started.
Step 1: Transmission fluid drains better at operating temperature, so let your car idle for a few minutes first. After turning your ignition off, raise and secure the vehicle. Then, lay down a tarp, some cardboard or a newspaper under at least a two-gallon catch pan. Next, remove the bolts from one side of the transmission pan, being cautious of hot exhaust parts and fluid.
Step 2: Gradually loosen the other bolts, which should allow the pan to tilt and begin to drain. Once all bolts are removed, lower the pan and dump the remaining fluid into the catch pan. Gently break the gasket seal with a screwdriver, if necessary.
Step 3: Clean the gasket surfaces on both the pan and the transmission housing. Inspect the pan for metal shavings or other signs of internal damage, and then clean it with solvent.
Step 4: Remove the old transmission filter and O-ring. The filter contains fluid, so keep the drain pan underneath.
Step 5: Install the new transmission filter, making sure that its O-ring seats in the appropriate orifice.
Step 6: Attach the new gasket to the pan with oil-soluble grease –not gasket sealer or adhesive.
Step 7: Refer to the service manual about using thread sealer on any or all of the transmission pan bolts, then screw in all fasteners finger-tight.
Step 8: Torque the pan bolts to spec in a spiral pattern starting at the center. Maximum torque is often about 12 pounds per foot.
Step 9: Lower the vehicle and fill the transmission with the recommended amount of fluid.
Step 10: Start the vehicle, warm it up, then shut it off and check for leaks. If you don’t detect any leaks, run the vehicle up to operating temperature on level ground, move the shifter through all gears, return to park and check the dipstick while the engine idles.
Always practice good safety behaviors when working on motor vehicles. To help prevent injuries, use appropriate personal protective equipment, which may include safety gloves, goggles, helmets and shoes.
Adding transmission fluid can sound daunting, but it is actually quite simple. Save a trip to the auto shop and some money by following this easy guide on how to add transmission fluid. We will also outline how to check your fluid levels, which you should do regularly to catch any potential problems early on.
Transmission fluid is what keeps your car’s manual or automatic transmission running smoothly, allowing you to properly shift gears. What you will need to check or fill your transmission is a clean rag or paper towel, a long funnel, and your car’s specific transmission fluid. Every vehicle is different — check your owner’s manual to see what type of fluid your car needs.
How To Check And Add Transmission Fluid
You must check your fluid levels while the car is warmed up to operating temperature. Some cars even require that you check it while the car is on and running. Refer to your owner’s manual to see if the car should be on or not. Regardless, the engine should at least be warmed up.
Your car should also be parked on a level surface to ensure you get an accurate reading on your fluid level. Put the vehicle in park and make sure your emergency brake is set.
(Before you get started, it’s worth noting that a few vehicles, such as some Ford-F150s, don’t provide under hood easy access to check your transmission fluid. Instead, on these vehicles, you must check and fill the transmission fluid by opening a bolt on the transmission itself. This is beyond the scope of this article.)
1. Locate the hood release and open your hood. The hood release can usually be found by where your left knee rests while driving. If you cannot find it, refer to your owner’s manual.
2. Locate the transmission dipstick. The transmission dipstick will have either a yellow/orange handle or it will be marked with writing or an icon. Do not confuse the transmission dipstick with the oil dipstick; they look very similar. If you are not sure, again, refer back to your owner’s manual.
3. Pull the transmission dipstick out and wipe it clean. You will need to wipe the dipstick clean so that you can properly measure the fluid level, once you reinsert it.
4. Reinsert the dipstick back to its original location and remove it again. This will show you your fluid level.
5. Check the fluid level on the dipstick. The fluid should be between the hash marks on the dipstick. If it is below the lower hash mark, you will need to add more fluid.
How To Add More Transmission Fluid
Next, it is time to add more fluid. First, make sure you check your owner’s manual to make sure you have the correct fluid for your specific vehicle and transmission. This is extremely important!
1. Place the funnel in the transmission check tube. The funnel will take the place of the dipstick.
2. Add the fluid in very small increments. It is important to add only a little bit at a time. You need to be careful about how much you are adding because you actually do not need that much. Remember, you can always add more, but it will be extremely difficult to take fluid out if you overfill the transmission.
3. Recheck the level with the dipstick after each pour. This will allow you to see how much more you need, and keep you from overfilling. When you reach a level that reaches the top hashmark, or the full marker on the dipstick, remove the funnel and return the dipstick to its original spot.