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Transaxle Fluid. Do I Change It Or Leave It Alone?

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by Lexington-76, Sep 13, 2024.

  1. Lexington-76

    Lexington-76 New Member

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    Hi All

    I’m trying to figure out if I should change my transaxle fluid or leave it alone. The manual say only inspect every 30,000 mile but doesn’t say when you should change it.

    I watch The Car Car Nut on YouTube and he advise (at least for the Lexus), that if you haven’t changed your transmission fluid before the 100,000 mile mark don’t change it and leave it alone. Well I’m at 100,000 and I’m trying to decide if I should change it or leave it alone. My assumption is that since the car is a Hybird that the transmission doesn’t work as hard compared to a normal gas engine car. Any advice here would be appreciated.

    Thanks
     
  2. BiomedO1

    BiomedO1 Senior Member

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    Welcome Lex;
    The car nut is speaking about a normal transmission with valve bodies and wet clutches NOT a hybrid CVT.
    I'm of the opinion that you should change it, just to remove the break-in wear material and other nasties floating around in there. Actually your transmission is working harder than a normal transmission, because of the two electric motors within. Your transmission may work independent of your ICE and move the car up to 10 mph before requiring the ICE to kick in.
    While the transmission on these cars don't fail too often, I just like to give it a leg up and consider it cheap insurance.

    Hope this helps....
     
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  3. ColoradoBoo

    ColoradoBoo Senior Member

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    I agree, go ahead with the change....it's as easy as doing an oil change BUT be ready for very tight hex bolts if they haven't been open in 12 years. (My Gen 4's have 10mm hex bolts.)
    I found it easier to snake a tube down the back of the engine bay to refill mine instead of pumping up the fluid...I hate those hand pumps.
     
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  4. bisco

    bisco cookie crumbler

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    if you are keeping the car long term, change it. if not, i wouldn't bother, these transaxles are almost bulletproof
     
  5. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    The type of work matters a lot.

    The Prius transaxle does not contain any clutches, bands, belts, drums or other friction systems. Therefore no particles are ever shed into the fluid.

    This is fundamentally different from most automatic transmissions, and it's the reason why these cars can go a zillionty miles on the factory ATF.

    If you do change it, insist on the real-deal Toyota WS ATF. I'm sure many other ATFs would provide the right lubrication, but personally I would not take the risk that they might eat the insulation off the windings of the motor-generators in there.
     
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  6. Mendel Leisk

    Mendel Leisk Senior Member

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    About one year or 10k is about right for that. Then you can leave it much longer, say once more at 100k or 10 years.

    @Lexington-76: yes, by all means change it. There’s a relevant link in my signature; on a phone turn it landscape to see signatures.
     
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  7. Lexington-76

    Lexington-76 New Member

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    Thanks Biomed01. I staring to realize that the Prius transmission or transaxle is a completely different beast and I’m still trying to understand it. By the way, what is ICE.
     
  8. Lexington-76

    Lexington-76 New Member

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    It’s standard operating procedure for me that I always have a new set of bolts on hand just in case. I recently attempted changed the front differential on my 4Runner and just couldn’t get it off. Had to take it to my mechanic and they practically destroyed the bolts getting it off. I’ll let my mechanic do it for me.
     
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  9. Lexington-76

    Lexington-76 New Member

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    How long we keep this depends on my daughter since it’s basically her car. However, I lost a Isuzu Trooper in the past because I didn’t keep up on the fluid changes. I’ve been a stickler on my maintenance ever since.
     
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  10. Lexington-76

    Lexington-76 New Member

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    Again I learned something new fro
    Again I learned something new from you Leadfoot. Thank you very much. This explains why the manual says only inspect. If I change it I plan on only using the WS ATF.

    By the way, does anyone know what the average cost is for one bottle of WS ATF goes for?

    Thanks
     
  11. Lexington-76

    Lexington-76 New Member

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    Thank you Mendel!

    This is very helpful! So generally recommend changing it every 100k or 10 years.

    Out of curiosity, has anyone ever experienced any transmission problems after changing the fluid. It’s seems with normal transmission, replacing the ATF on older transmission can potentially cause problems but from what I’ve read here this doesn’t appear to be the case with the Prius. Is this correct? It also seems the procedure for this is a simple drain and fill with no special procedure or tools correct?

    Thanks
     
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  12. Mendel Leisk

    Mendel Leisk Senior Member

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    Dealership parts department. Ditto for the fill/drain bolt washers.

    BTW, just woke up, to you’re having a Prius c. Still, the procedure should be very similar. You might want to take out a short term subscription at Toyota Tech Info, get the precise instruction. It may not exist; Toyota did NOT provide an instruction for Gen 2, but they do for Gen 3 and 4.

    My hunch, it’ll be fine. For sure fill with the car level till it starts coming back out, you’re good.
     
    #12 Mendel Leisk, Sep 15, 2024
    Last edited: Sep 15, 2024
  13. sylvaing

    sylvaing Senior Member

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    Like others have said, the Prius eCVT transmission is completely different than a normal car transmission. Beside the two electric motors, it has just metal gears and bearings. Metal particles shed by the gears are caught by a magnet at the bottom of the transmission case but, in this transmission, you can't access this magnet so even if you change the transmission fluid, they'll all remain on the magnet. Basically the only thing that could be floating in the fluid is the motor winding insulation but if you have that, you have a bigger issue lingering.
     
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  14. ColoradoBoo

    ColoradoBoo Senior Member

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    Lexington: ICE stands for Internal Combustion Engine. It's how Hybrid folks differentiate when talking about engines...kinda like how motorcycle riders call car drivers "cagers" Electric engines can have all kinds of different names but Toyota seems to like electric motor generator or MG...I'm not certain but believe all Prius' have an MG1 and an MG2. You may see traction motor or generator motor (or both in a Honda).
    A quart of Toyota WS is between $5-9 a quart...my 2017 took 3 3/4 for the service. I bought 5 so will only need to buy 3 when I do my 2021 Prius which is coming up on 50,000 miles.
     
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  15. BiomedO1

    BiomedO1 Senior Member

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    My 2012 Prius C took a bit more than 3, so I'd grab 4 quart to be safe. Your correct, those fill and drain plugs are very tight out of the factory. They're only suppose to be 37 ft/lb. If you do it yourself, 10mm hex socket w/1/2in breaker bar and scrape all the dirt out of those hexes with an ice pick, before trying. Plant the socket in firmly and push or stomp on it.

    Hope this helps...

    FYI: those electric motors in the tranny are also chargers for your batteries and starter for your engine - so a critical component of that car.
     
  16. Mendel Leisk

    Mendel Leisk Senior Member

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    Since the value may be used for torquing: with Gen 2 and 3 the Repair Manual spec is 29 ft/lb. With Gen 4 it's 37 ft/lb. That's all I've got, haven't got the Prius v or c.

    Unless OP checks on Toyota Tech Info, looks up the Prius c info, probably best to stick with 29 ft/lb. Which is still tough to bust loose. Again, I go straight to an over-long ratchet I have (about 18" from fulcrum to end of handle), With a reducer to 3/8" drive and a proper 10 mm hex driver "socket".

    You definitely don't want to use a L-shaped hex key with a pipe extension. Doubly so, don't try a 3/8" instead of 10 mm.

    BTW: Honda uses a similar socket head cap screw on their transmission drains, but with a 3/8" square recess. I remember over 40 years ago, very green, going to attempt changing the transmission fluid on our '81 Civic: saw that, phoned up the dealership, and asked what special socket was required. The guy went down to the shop to ask a mechanic, got back to the phone and told me something like "they just use a 3/8" drive ratchet wrench without a socket". :)

    See attached Repair Manual excerpts, for aforementioned torque values, and just to get a feel for what's involved.
     

    Attached Files:

    #16 Mendel Leisk, Sep 15, 2024
    Last edited: Sep 15, 2024
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  17. sylvaing

    sylvaing Senior Member

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    And car drivers call motorcycle riders "organ donor", which is a sad reality unfortunately..
     
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  18. pasta4breakfast

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    You should be able to find it for $11-14 per quart. Buy it online at the website below. Put in your zip code and you can check the special prices different local dealerships are offering. It will likely be cheaper than the price they quote you over the phone or in person.

    World Standard Automatic Transmission Fluid
     
  19. douglasjre

    douglasjre Senior Member

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    I've been using Valvoline max life dex/merc6/LV in multiple pri over the past 15 years. Haven't had any failures in any of them. It's not the same thing as WS but how different I'm not sure. It's like $10/gal. Many of the pri r subjected to severe duty every day pulling trailers at full throttle. You decide. I'm ok w subbing max life 6. You decide what you're comfy w. I change it every 50k
     
  20. ColoradoBoo

    ColoradoBoo Senior Member

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    Sad but too close to reality. I gave up my motorcycle days about 15-years ago (too many close calls with stupid drivers here).

    My son-in-law has been wanting to buy a motorcycle until last week. He had a 22-year old co-worker get killed while riding his bike....very sad.