How to Change the Transmission/Transaxle Fluid
2004-2009 Toyota Prius


Before doing anything read my disclaimer & safety info.



A transmission/transaxle fluid change is a routine maintenance item, just like an oil change but performed much less often. The first time Toyota recommends replacing this is 120k if you're driving in "ideal conditions," although they recommend inspecting it every 30k. Based on what I've read on the forums and other Prius sites 60k may be a better interval for routine changes. Since I bought my Prius used I didn't know if this was ever done, but now at 115,600 I wanted to change it to get a reference point.

I did this after doing an oil change in the middle of a MN winter and have to say that it was really simple. I will be going into detail below but this really boils down to: raise car, remove fill plug, remove drain plug and drain fluid into container, torque drain plug, add new fluid, torque fill plug, lower car.

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Tools Needed:

Parts/Supplies Needed:


1) Put you car on ramps or jack up the front and place the car on jack stands so you have some room to work underneath the car. Follow steps 1-2. You will also want to put some newspaper or a drop cloth underneath the transmission case so you don't get your floor/driveway dirty if any spills occur.

2) Here's the transaxle case, circled in RED is the drain plug and circled in GREEN is the fill plug. Looking at this picture (taken from underneath looking straight up) the fill plug faces the front of the car and the drain plug is angled down to the ground. The transaxle case is on the drivers (left side of the car) whereas the oil pan is on the passengers side of the car. Another perspective. Hobbit also has a great picture here to give you an overview. So now that you know where it's located....

2a) Use a 24mm socket to unscrew and remove the fill plug, circled in GREEN. Depending on temperature and if the car's warmed up you may or may not hear a hissing sound, this is normal. If you've put your car on ramps no fluid should come out as the car is on an angle and fluid is therefore lower than the bottom of the fill hole.

3) Position your drain pan under the trans drain plug. Use a 10mm hex socket to remove the trans drain plug (circled in RED in the previous pic). To avoid a mess, first crack the plug so you can turn it by hand. Then remove the plug by hand while keeping upwards pressure so the plug doesn't fall out. You'll feel it "jump" a thread once it's completely unthreaded, at this point quickly pull it out and the fluid will burst out! My pic is a trickle since it took me a bit to grab the camera, it comes out fast.

4) While the trans fluid is draining pop the hood and remove the front engine cover. You need this off so you can get a funnel snaked down to the transmission fill hole.

So here's what my drain plug looked like after I took a swipe at it before realizing I should show how dirty it was...opps! Anyway, it wasn't too bad so maybe the previous owner had a trans change at some point. Either way a lot of junk was cleaned off. Also note how the crush washer "crushes" in to fill voids, you definitely want to use a new one each change.

5) Clean up both plugs and install a new crush washer on each one. Reinstall the 10mm hex drain plug and torque it to 29 ft-lb (39 Nm, 400 kg-cm).

6) Run your funnel down from the top of the engine bay and into the front fill hole of the transaxle casing. This pic is shot sideways looking straight up, front of the car is on the left.

Here's another perspective looking top down.

I wanted to know how much fluid drained out so I would know how much to put back in. So I marked my container as shown with some tape.

And here's what I got, almost one gallon. The repair manual calls for 4 quarts so this is good. Bring the used fluid to your local recycling center. I like these containers but the caps don't stay on well so I duct tape them before transporting to the recycling center, a trip made maybe every year or two.

7) Add Toyota ATF WS transmission fluid; I put in about 3.75 quarts. The repair manual says 4.0 quarts but 3.75 seemed about right for me to get to about the level I felt when dipping my finger into the fill hole before I drained the fluid.

NOTE: If want to do this completely by the book your car needs to be on a level surface and the fluid level should be within 0-5mm of the bottom of the fill hole. Essentially, you add fluid and if it starts leaking out it means you're at the 0mm mark and it won't take anymore.

Use your judgment on how much to add, I would suggest some type of jug to measure how much came out like I did so you know roughly how much to put back in. A used 1 gallon milk jug would work nicely if you don't have a large 5 gallon container like I do.

8) Install the 24mm fill plug with a new crush washer and torque it to 29 ft-lb (39 Nm, 400 kg-cm).

9) Turn off the Maint Req light (if it was on due to this) and reset your trans fluid counter on your MFD. I also record mileage and date the job was done in a OneNote notebook.





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Last revised: Sunday, 29-Oct-2023 16:37:00 EDT