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Gen4 Prius Transmission Fluid Change

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by High Mileage, Jan 26, 2020.

  1. High Mileage

    High Mileage Active Member

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    I just completed changing the transmission fluid on my 2018 Gen4 Prius Prime Advanced. I did this at 34K miles to gauge fluid condition and help me establish what kind of interval I think I want to follow. I understand that this fluid is intended to be "Lifetime" and does not have a listed maintenance interval. This service should be the same for any Gen4 model Prius with the P610 transaxle. The fluid I drained out looked very good in my opinion based on my previous Gen3 which I was changing fluid every 60K miles. I purchased the Gen3 with 60K miles so it was the first time I had to look at the fluid. This vehicle I purchased with 12K miles on it and 30Kish seemed like a good time to take a look. I know fluid condition is purely an opinion without having it analyzed etc. etc. This was a good way for me to look at the fluid and develop an opinion and maintenance strategy for me.
    upload_2020-1-26_11-44-18.png
    You will need:
    Flat blade screwdriver for removing the 10 clips that secure the plastic engine shield.
    10mm socket and ratchet for removing the 4 bolts that secure the plastic engine shield.
    10mm hex drive socket for removing/installing the drain and fill plugs on the transaxle.
    4 qts of Toyota WS transmission fluid.
    Gear axle pump for filling the transaxle.
    Drain pan to catch old fluid.

    I have the luck of having a lift at my house, but I suggest that this can be done safely using jack stands and a jack at home, just more work and effort needed.
    With the vehicle safely supported above the ground remove the 4 bolts and 10 clips that secure the plastic cover under the engine/transaxle.
    upload_2020-1-26_11-52-0.png
    Using the 10mm hex head socket remove the drain plug at the center of the transaxle and catch the fluid in a drain pan.
    upload_2020-1-26_11-46-7.png
    upload_2020-1-26_11-48-24.png
    Reinstall and torque the drain plug. I reused the aluminum washer with no issue.
    Remove the fill plug on the right side of the transaxle, passenger side for us in the USA.
    upload_2020-1-26_11-53-17.png
    Using the gear oil pump refill the transaxle with WS fluid. It should take approximately 3.25qts to refill. With the vehicle level fluid should start to overflow the fill plug. Measuring what you take out should provide a very close amount for what needs to go back in.
    upload_2020-1-26_11-54-44.png
    This is what drained out of mine.
    upload_2020-1-26_11-53-54.png
    upload_2020-1-26_11-56-4.png

    Install and torque the fill plug. Re-install the plastic underbody shield. Drive and check for leaks.
    Hope this helps folks in the future.
     

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  2. Raytheeagle

    Raytheeagle Senior Member

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  3. Elektroingenieur

    Elektroingenieur Senior Member

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    Thanks for sharing your technique and photos.

    I’d add that the Repair Manual (more info) has two procedures for changing the hybrid transaxle fluid: an “adjustment” procedure, in which the fluid is drained and refilled once, as kindly described here, and a “replacement” procedure, in which the fluid is drained and refilled, the engine is idled in maintenance mode for 30 seconds, and the fluid is drained and refilled twice more. Obviously, there’s no need to do the latter unless you’re trying to purge the transaxle of contaminated fluid.

    In these procedures, and in the one for inspecting the fluid level, the manual says to use new gaskets (Toyota part number 90430-18008) when reinstalling the filler and drain plugs for the last time. The torque specification for both plugs is 50 N·m (37 ft.-lb.), and for the No. 1 engine under cover bolts, 7.5 N·m (66 in.-lb.).
     
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  4. Mendel Leisk

    Mendel Leisk Senior Member

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    How about "some method for getting the new fluid in". A simple alternative is a funnel from above, with hose extension.

    And you're probably fine. But personally, I would change it. As @Elektroingenieur says, if doing multiple fluid changes, change it just on the last one.

    Yeah that's the key. Don't sweat how much came out, how much went in. Just have the car level when filling, and fill till it starts coming back out. Foolproof.

    The transaxle fill and drain bolts I pay attention, torque to spec. With low torque "locator" bolts, I'll often just hold a ratchet wrench with one hand, over the fulcrum, twist fairly firmly.

    My one gotcha: I tend to install the cover bolts loose, so the cover is free to shift as I install the plastic fasteners. Then I go back and tighten the bolts. I have forgotten the last step, and lost one bolt due to that.

    I made a gizmo, mostly used for tightening the undercover bolts, convenient and acts a torque limiter:

    IMG_1941.JPG
     

    Attached Files:

    #4 Mendel Leisk, Jan 26, 2020
    Last edited: Jan 26, 2020
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  5. Salamander_King

    Salamander_King Senior Member

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    Thanks for sharing this for PRIME with nice photos.

    One thing I may add that I have read on Gen3 transaxle fluid change is to remove the FILL PLUG before you remove the DRAIN PLUG. This is so that just in case you have trouble removing the fill plug. If you drain the fluid first and can't refill it, you need to tow your car to get it serviced somewhere else.
     
  6. Chazman62

    Chazman62 Member

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    Re: "It should take approximately 3.25qts to refill."

    Is that approximately how much drained out?

    Any idea what the total fluid capacity (volume) might be on this Prime transmission?
     
  7. Mendel Leisk

    Mendel Leisk Senior Member

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    I believe 3.8 US quarts at refill. From the attachment in post #4:

    upload_2020-1-27_8-18-25.png
     
  8. Laura-Ann

    Laura-Ann Junior Member

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    I will likely hit 20K miles in my 2019 Prius Prime sometime in the next 3~4 weeks, and am planning to change to do the first transaxle fluid change myself. This is a lot sooner than the 60K factory recommendation, but it gets really hot where I live in the summer months, and since that fluid both lubricates and cools not only the gears and bearings, but also the MG stators and rotors, I figure it can't hurt to invest a little extra $$ to protect the transaxle. Just replacing the MG2 stator is supposedly almost $2,000 if it gets cooked, and contaminated fluid is listed as a high-probability cause of stator failures in the Toyota HSD transaxle. I'll change it at 40K intervals after that, unless I see from this fluid change that I should be doing it more often. I have a couple of questions: 1. What diameter are the plastic push-rivets for the engine shield? I went to buy a package of them on Amazon in case I break one or more of them, and found that there are at least 4 different sizes. Which size do I need to buy? 2. All of the instructions I've seen say that I have to pump the new fluid in. I don't own a pump. Is there some reason that I can't get like 5 or 6 feet of 1/4" vinyl tubing hose and a funnel, thread the hose down to the transaxle fill hole from somewhere above the engine, attach a funnel to the hose, and just pour the new fluid in via gravity? Thanks!
     
  9. Salamander_King

    Salamander_King Senior Member

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    Humm, AFAIK, there is no factory recommendation for the transaxle fluid change.
     
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  10. Mendel Leisk

    Mendel Leisk Senior Member

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    Same here.

    Still, sooner than later is good. My 2 cents: change it at one year mark or 10k miles, whichever comes first.
     
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  11. Salamander_King

    Salamander_King Senior Member

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    Yeah, I did it on my Gen3 at 30K then thinking to keep the car for a long time. Then came Prius Prime. There is no way I will be keeping my current PP longer than 3 years. I am not going to bother with anything outside of Free ToyotaCare.
     
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  12. pnw_jk

    pnw_jk New Member

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    I'm wondering if there is any necessity to replacing the fluid twice?
     
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  13. Raytheeagle

    Raytheeagle Senior Member

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    I was thinking about doing a second change soon as I am now at 54k miles;).

    If I do, I'll post up what I find(y).
     
  14. High Mileage

    High Mileage Active Member

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    I am now at ~95K miles and I plan for another change of fluid at ~100K. I think a change every 60K miles or so will continue to be my target depending on how it looks on this second change.
     
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  15. BiomedO1

    BiomedO1 Senior Member

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    60K mile ATF changes is the industry standard for wet clutch transmissions; 25K-30K if your towing - dependent on load capacities. No wet clutches in these transmissions; means less contaminates - cooling and lube is the main function of this ATF.
    My first ATF change on my old 2013 Prius C was pretty dark @ 25K. Second change @ 75K was pretty clean - could probably stretch it out to 75K - 100k intervals w/o any issues - unless your climbing mountains or towing. That's been my experiences, based on my driving style and habits. This new PP will get the same treatment.

    PS. Always loosen the fill plug FIRST!!! Don't drain it, if you can't fill it. If you don't have a new aluminum washer, just flip it over and torque to specs. They usually squeeze down and seal for 3-4 changes - this is from experience, but it should be changed and torqued properly. If they are over-torqued, they won't seal the next time you try to reuse it. If you don't have a "good" torque wrench; buy one.

    Hope this helps....
     
    #15 BiomedO1, Mar 3, 2022
    Last edited: Mar 3, 2022
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  16. Salamander_King

    Salamander_King Senior Member

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    I only did drain-and-fill transmission fluid change twice. Once on my Gen3 at ~30Kmiles and once on my 2017 PP at ~36km, but I sold both cars shortly after that. I have not bothered with the transmission fluid on my new PP so far. The 2020 PP was sold at 10mo old and 4Kmiles, and the current 2021 PP is still at 7 mo old less than 5Kmiles. I don't think I will be keeping my current PP long enough to be needing the transmission fluid change.

    That is not the case for my son's Honda. It has some kind of sensor that triggers the Maintenance Minder code. I first thought that was strictly based on the miles driven, but lately, I found out that is not the case. I did CVT drain and fill on it ~15monts, 20Kmiles ago. The Maintenance Minder is now showing code B13 which is engine oil and filter and transmission fluid change. Yep, some cars require far more frequent transmission fluid change than our PP.
     
    #16 Salamander_King, Mar 3, 2022
    Last edited: Mar 3, 2022
  17. Salamander_King

    Salamander_King Senior Member

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    I think you mean "Always loosen the FILL PLUG FIRST." Not the DRAIN PLUG.
     
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  18. BiomedO1

    BiomedO1 Senior Member

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    Yes, Honda has factory specific intervals for their CVTs

    For other cars with NO factory specified ATF change intervals, 60K miles is a good place to start and is cheap insurance.

    BTW: OEM factory lifetime fluid specification really means - When your OEM warranty expires!!!!! NOT your car or your lifetime.....:D
     
  19. Salamander_King

    Salamander_King Senior Member

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    It's not specified interval parse. There is no mention in the manual as to the miles or months interval for the service. Rather, the reminder comes up as a Maintenance Minder service code. I once asked at the Honda Forum about what triggers the Maintenance Minder to show specific code, especially for the subcode for the transmission fluid, but could not find an answer. It does the same thing with an oil change service. It is not strictly time or miles-based as in a Prius. There has to be some type of sensor that is monitoring the quality of oil or transmission fluid, but I don't know how that works. On contrary, our Nissan Pathfinder has a specified 30Kmiles/3yr interval for transmission fluid change. BTW, Nissan Pathfinder (and I think for most other Nissans including the Leaf) also has specified brake fluid change for every 20Kmiles/2yr, which is by far the most frequent fluid change interval (aside from engine oil) of any kind for any car I have owned so far.
     
    #19 Salamander_King, Mar 3, 2022
    Last edited: Mar 3, 2022
  20. Mendel Leisk

    Mendel Leisk Senior Member

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    I’m thinking it uses readily available sensors, maybe engine coolant temp, ambient air temp, rpm, maybe also counts start-ups, then does the countdown to next service slower/faster, depending on factors it's gleaned.

    I suspect it goes through the extras, things like coolant and transmission fluid changes and so on, in a preset sequence. But tailors the intervals somewhat, to reflect what it's getting from the sensors. Similar to regular vs severe service.

    In my experience it would invariably alternate between A1 and B1 services, those being rotate tires plus oil change and oil/filter change respectively. B1 also included a brake inspection. And there'd be extra numbers for additional once-in-a-while services.

    More info on the schedule in the attached, an excerpt from one manual I had, for our daughter's 2010 Pilot.
     

    Attached Files:

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