Changing Transaxle oil

Hi Bill,

This is pretty easy to do. You will need 4 qts of Toyota ATF WS (should cost ~$8 per quart) and two replacement aluminum washers (around $1 each.)

The needed tools include a ratchet wrench along with a 24 mm or 15/16" socket to remove the fill plug and a 10 mm Allen hex key socket to remove the drain plug. You also need a funnel with a three-foot long tail to reach the fill plug, which is on the side of the transaxle facing forward.

If you have the proper tools and funnel, it is quite easy to replace the transaxle fluid. Make sure that you loosen the fill plug first, to clear the partial vacuum (when the transaxle is cold) and ensure that you don't have problems with a stuck fill plug. When draining, make sure that you don't inadvertently drain the inverter coolant instead of the transaxle oil. (This is one reason why the drain plug uses a hex key.)

Place the funnel near the inverter and snake the tail down to the fill opening, then add the new fluid. Tightening torque of the drain/fill plugs is 29 ft.-lb.

 

The dealer I went to charged $60 ($20 part and $40 labor). Maybe you should try another dealer?

I don't have the tools and the complex I live at does not allow any work in the parking lots. So $60 every 60k miles isn't a big deal for me.

 

I would also suggest that you "drop" the pan when changing the oil. This would drain a bit more of the old stuff, plus you will get a chance to look inside for sludge and to make sure the oil pick-up screen is clean. Dropping the pan requires a new gasket that costs under $20 (forgot exactly how much) from your local dealer's part dept. or better yet - over the net from an online Toyota dealership, if your local one is expensive.

As Patrick said, a fairly easy DIY job if you are into this kind of thing.

There is no separate differential oil to change (for instance, on some 4 cylinder Camry while the oil is the same the differential and the transmission must be drained and refilled separately).

 

Sad to say but the 2004-current, NHW20, Prius do not have a transaxle pan to drop. That exists only for our older 2001-03, NHW11 Prius.

Bob Wilson

 

Hi Bob,

Fortunately the NHW20 transaxle seems to be more robust compared to NHW11 in terms of not producing excess metal debris. When I changed the fluid on my 2004 at ~30K miles there was only a tiny amount of fine ferrous powder on the tip of the little magnet on the drain plug. Compare to the large qty of debris that can be found on the rectangular magnet and the drain pan when the pan is dropped on NHW11.

For those changing fluid on NHW11, the tightening torque on the drain plug is 36 ft.-lb (since the pan is steel, vs 29 ft.-lb on the fill plug) and the torque on the small drain pan bolts is 67 in.-lb. The drain plug has a hex head and does not need the Allen key. 5 qts of Toyota ATF T-IV are required.

 

Ahhh... my bad about the pan or lack thereoff on the '04+

 

When it begins to flow out the filler hole, it is full. The Toyota manuals show some impossible 2-3 mm below the filler hole, something that would require a 90 degree mini-dip stick. My rule of thumb, if you can feel the oil sticking your small finger into the hole, it is perfect.

Bob Wilson

 

Hi Bill,

As Bob W. said, your finger is the dipstick. If you can feel oil, this is good. Otherwise, raise your car so that it is level and fill until the fluid starts to seep out of the fill hole.

Hi Bob W.,

I helped a PTS member in Orange County change the transaxle fluid in his 2002 this morning. He will be sending a sample to you (ATF WS with ~3K miles; transaxle/inverter recently replaced, dealer used WS instead of T-IV.) We replaced with ATF T-IV per specs. The WS fluid level was perhaps 1/2 qt low. Transaxle pan was quite clean as you would expect for a new transaxle, a minor amount of ferrous filings on the magnet.

Hi ScottY,

You have a great dealer, if they will do the transaxle fluid change for $40 labor. Some dealers practice "value" pricing well into three digits, like Bill mentioned in his initial msg. The ATF WS costs ~$5 per quart, hope they installed new washers!

 

Hi Bill,

I think that group members have become sensitized to the desirability of changing transaxle fluid periodically due to the number of Classic transaxle failures and the results of used oil testing. 2G transaxle failures are relatively rare; nevertheless the oil change is relatively easy to do once you are set up to do it, and I recommend this practice. It feels good to drain out the murky used oil and add clean new oil with a bright red color.

ATF WS is very thin oil. So thin that if you spill some on your concrete driveway, it will hose off without need for scrubbing etc.

When shopping around locally for ATF WS, the Irvine Toyota parts dept clerk also told me that there's no need to change the fluid prior to 100K miles. My local dealer, Rancho Santa Margarita Toyota, wanted ~$9 per quart, above MSRP. I ended up buying a case from Tustin Toyota, at $5.20 per quart (MSRP). So, it may pay to call around.

Have you decided that you will DIY or are you still looking for a dealer to perform this work for you?

 

Thanks Patrick for posting the helpful information. I just wanted to add that it is definitely a 10mm hex key that is needed to loosen the Transaxle drain plug. And as you mentioned, a 15/16" socket fits the 24mm side fill nut perfectly (my conversion calculation gives about 23.8mm for 15/16", so I was concerned it might not fit a 24mm nut, but it fits very well with just a very small amount of play).
Also, as you and others have mentioned, it pays to shop around for the Toyota WS ATF. One dealer (Lake Norman Toyota -- Charlotte, NC) charges $4.19 / qt while the other big dealer (Scott Clark Toyota -- Charlotte, NC) charges $5.20 / qt.

 

I'm glad that you changed the transaxle fluid successfully. What odometer reading are you at, what did the old fluid look like, and how much debris did you find on the drain plug magnet?

Did you use the funnel w/long tail or did you devise some other refill method like a pump or squeeze bottle?

I've noticed that larger SAE sockets seem to cost much less than similar-sized metric sockets (like Sears Craftsman for example) so if an SAE socket will do double-duty for a metric size, all the better.

Patrick Wong

 

Not sure how relevant this is to the Prius setup, but I have a related question. When changing the manual transaxle fluid on my 2005 Scion xA, there was a similar setup where the fill plug faced directly forward on the car. With this configuration, it was exceedingly difficult to get the oil into the hole without it running out and going all over the place. Only after I completed the job did I discover that there was a 'reverse sensor' on the top of the transaxle that could be removed for easier filling. Is there something similar on the top of the Prius transaxle that would make the job a bit easier?

 

The inverter blocks easy access to the top of the Prius transaxle. If you removed the inverter then you would find another access plug that could be removed for fluid filling purposes. However removing the inverter is much more difficult than making a suitable funnel with a 3 ft long tail.

 

Patrick-- Thanks!
The odometer was at 66040 miles when I changed out the transaxle fluid. The fluid still had a red tinge but was pretty dark. The magnetic plug had a 2mm thick layer of fine iron shavings stuck to it, which I cleaned off before replacing the plug. I used two new aluminum washers (which were $2.22/each at the dealership -- yikes), one for the drain plug and one for the fill plug. They were the same part number according to the guy at the parts counter. For the new fluid I used Toyota ATF WS which was $4.19/quart from the dealership. Total amount added was about 3.9 quarts.
To refill, I used a funnel with a long hose attached. The maximum hose outer diameter is about 0.5 inches -- any larger and it won't fit into the side fill port. There is no need for a large diameter tube anyway because the ATF is so thin that it will pour quickly through a narrower tube.

 

Here are three pictures (attached thumbnails below) of the transaxle fluid change:
Draining the fluid (somewhat red after 66k miles)
The plug before cleaning off the iron shavings
The plug after cleaning

 

Nice photos. I would say that the shavings are extremely fine, like powder. Would you agree?

If the metal debris accumulated on the magnet is larger than powder, then I think it is time to worry about the longevity of that particular transaxle.

You got a great price on the transaxle fluid, so that helped offset the price of the aluminum washers.

 

I first did mine at around 12,000 km, my magnet looked the same. Subsequent changes, the magnet stayed far cleaner