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.
     

    Attached Files:

  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.
     
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  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
     
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