Toyota Prius 2004 Transaxle/Transmission Fluid Change Necessary?

Trans fluid change according to Toyota is not necessary for the life of the car. But if you want your car to have a longer life, change it at least once because it's good preventative maintenance. Toyota's definition of life of the car has more to do with selling you a new car than maximizing the life of the old one. As for Mass Air Flow sensor, I'm not sure, but I'd wait for it to be an issue first and I'd instead be focused on cleaning intake manifold rather than just that one sensor.

 

I'm not sure how a hybrid battery installer would be the best adviser. That said:

I wouldn't hesitate to change the transaxle fluid. You can get replacement washers for the drain and fill bolts, at a Toyota dealership parts department. I believe 2nd gen spec is approx. 3.5 quarts/liters of Toyota ATF WS fluid. I'd recommend to stay with that; Toyota is quite adamant in the Owner's Manual, to use that fluid, and nothing else, or risk damaging the transaxle. Others may be along shortly to debate that. Level is correct if you refill with the car level: when it starts coming back out it's correct. The easiest way I've found to get the new fluid is to run hose down from above, connect a funnel to it. Just go slow once you've gone past 3 quarts added. Don't retain any spilled fluid, and dispose of the remainder, Toyota cautions to not store opened bottles and use later, kinda like brake fluid I think.

Unlike a conventional automatic transmission, the Prius transaxle drain and fill replaces virtually all the fluid in there, and is the best thing you can do for it. A little late now, but my 2 cents: the optimum time for first change is around the one year mark and/or 10K miles. Then maybe a second after another 30K miles, and maybe one more after another 60K miles. In my experience, every successive drain and fill, regardless of stretching the interval, the drain fluid was progressively cleaner. The first drain, around the one year mark in my case, was by far the darkest. In short: it's always darkest before the first drain.

The MAF sensor: yeah I would look before leaping. For sure get the specialized cleaner, CRC's MAF sensor cleaner is one.

 

You only need 1 o ring there is none on the fill plug. 3.9 qts of transmission fluid is the amount you will need. They said that transmission fluid was lifetime on my Tacoma pickup also then changed it to 60,000 miles later. It’s best to change it. You should clean the MAF also. They make a special cleaner for it but I use carb cleaner myself. I pretty much think of cleaning it as part of a tune up on my Toyota’s

 

Or it's missing on yours? Take a look at this second gen Prius transaxle fluid change instruction; there's a picture about halfway down with both bolts, and washer on each:

Toyota Prius: How to Change the Transmission/Transaxle Fluid - PriusDIY.com

Good instruction btw. The 2nd Gen Repair Manual doesn't seem to have anything.

 

Well the one they gave me did not fit, and they gave me 2 of the same one. It fit the drain plug perfectly the fill plug was a larger diameter. Plus mine had never been changed and did not have one. Have you ever seen one on a 2nd gen?

 

The topic is "Necessary?"... the answer is NO. Advisable? Yes.

These cars DO NOT have a "transmission", there is no torque converter, clutch(es), drums, synchronizer(s), or sliding components that would make it a "transmission". There is a set of planetary gears, but they are constantly in mesh like one would have in a differential and the potential for wear is small, especially if you do not get it stuck (mud/snow for example) where the differential would spin-up.

Is changing the fluid a good preventative measure? Sure.

As for CHANGING the MAF sensor, that is just silly.

 

Cleaning the MAF sensor is practically free. I would suggest that.

 

Just make D@MN SURE that electrical contact cleaner is used and not some other solvant (brake-clean, ether, etc), although denatured alcohol can work.

 

Not in the flesh, but it's shown in my above link. Here's the image:



Looks like fill bolt on the left, and slightly larger diameter washer.

 

And yet his write up says to use the same two washers I got from my Toyota dealer???

I have a 2006 perhaps they did a production change, I don’t know. What I do know is I have actually been under the car and did the job. It didn’t fit.

 

Yeah when I lay a ruler on them on my screen (funky but effective) they both measure about the same OD.

I see an 08 video, he says the two washers are the same on his. Yeah maybe the different years.

 

I had a 2004 and have a 2007, and the washer is the same diameter for the transaxle ATF drain and fill plugs.

OP should definitely replace the transaxle ATF using 3.9 US quarts of Toyota ATF WS.

Use mass air flow sensor cleaner. Remove the MAF from the air cleaner housing, then apply the spray liberally. Do not touch the sense wires in the MAF.

 

Agree, I currently maintain an '05 and '07. The aluminum crush washer (90430-18008/90430-A0003) goes on both drain and fill plugs for transaxle and drain plug for inverter coolant loop. Same deal with turd gen.

This is a puzzler... Perhaps your Toy parts sold you the steel or copper-ish washers? Regardless, the stamped alu washer belongs on both drain and fill plugs. Pretty sure diameter and thread pitch are the same on both drain and fill, too...

 

I will look at the part number on Monday. It was an aluminum washer though.

 

I have a 2005 Prius with 248,000 miles. Have never changed the transaxle fluid.

Last year I thought the hybrid battery was going bad. All signs pointed to it: Poor mileage etc.

When I went in to have a new battery installed, the owner of the garage said your battery is fine, all you need to do is clean the Mass Airflow Sensor.

I bought a can of the Mass Airflow Sensor spray at AutoZone, cleaned the sensor, and the battery is working great. The car is just better running overall.

I was prepared to spend $1100, and ended up spending $10.

 

Lol.