Does 2012 Prius Two have a differential?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by indel, Oct 20, 2025 at 9:12 AM.

  1. indel

    indel Junior Member

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    I found some references to there being a differential, but I also read that it is integrated into the transmission. So I assume it does not require gear oil. Can someone confirm?
     
  2. Mendel Leisk

    Mendel Leisk MMX GEN III

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    There's no separate differential, no distinct gear oil replacement. Maybe download the pdf of the Toyota publication "Warranty and Maintenance Booklet". One source, under the "Manuals" tab. All the fluid changes Toyota wants are noted in there, albeit in hard-to-read, event-by-event format. Attached is a spreadsheet summary I've put together, both as-is, and extrapolated to 240k miles (Toyota stops at 120k).

    What's the miles on it now, btw? I'd also consider these, mostly not in the Toyota schedule services:

    EGR cleaning
    Transaxle fluid change
    Brake fluid change
    Brake inspect/clean/lube (sort of in the schedule, very understated though, every 30k miles, but oft ignored)
     
    #2 Mendel Leisk, Oct 20, 2025 at 11:41 AM
    Last edited: Oct 20, 2025 at 11:47 AM
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  3. ChapmanF

    ChapmanF Senior Member

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    Pretty much all front-engine, front-wheel-drive cars combine the transmission and differential into a single contraption, and call it a 'transaxle'.

    The places you drain and fill the transaxle oil cover the whole works.
     
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  4. indel

    indel Junior Member

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    Thanks Mendel for very useful information. This Prius has 142K miles. I have not found anything wrong with it prior to purchase. It was PPI at the local Toyota dealership. I specifically asked them to check hybrid battery health and the EGR system function. This was their response posted to the Toyota owner's service history:

    "CUSTOMER STATES ~|~CHECK EGR AND HYBRID BATTERY ~|~ ~|~BATTERY STATE OF CHARGE WAS WITHIN SPECIFIED RANGE, EGR SYSTEM WAS FUNCTIONING AS INTENED, NO FAULTS PRESENT"

    Which, needless to say is not very helpful. The tech told me on the phone that they don't have tools to do any further diagnosis which I found hard to believe.

    The place I bought it from did an oil change and replaced the rear rotors and pads, so I assume they also bled the brakes. I think we can safely assume they did not use Toyota parts or fluids for any of this.

    My plan is to do the following before the winter sets in:

    Diagnosis
    -----------------------
    - Battery health and life expectancy with DrPrius
    - 12V battery test
    - EGR trace live and static (haven't figured this out yet)

    Service
    -----------------------
    - Oil change with Mobil1 full synth 0w20 and Fram ultra filter
    - Transmission oil drain and refill
    - Coolant drain and refill on ICE (haven't yet figured out if inverter coolant can be drained easily like the ICE)
    - PCV valve
    - Air filters
    - Spark plugs

    Unless I start seeing some symptoms of overheating, I don't want to get into water pumps and EGR cleaning until next spring.

    One of the problems I am having is locating correct part numbers on Toyota's website. I find myself coming back to Priuschat to find numbers and when I enter those on toyota's website, it often tells me that it's incompatible with my VIN. How do you guys deal with this problem?

    For example, there are two different water pumps, one for ICE, another for INVERTER, but I can't seem to locate the correct part numbers for either.
     
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  5. Mendel Leisk

    Mendel Leisk MMX GEN III

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    With 142k I wouldn't bother "diagnosing" the EGR, it'll be pretty clogged. Note too: there are crucial EGR passages in the intake manifold. I'd also start researching head gasket replacement (protracted neglect of EGR cleaning and head gasket failure seem to go hand-in-hand), and keeping an eye on the engine coolant reservoir level. The head gasket failure mode is typically coolant leaking into combustion chambers. Typically starts with cylinder one.

    More info on EGR cleaning and head gasket in my signature. (if you're on a phone, turn it landscape to see signatures.)

    Also would be very timely to change the engine water pump and thermostat. The generic name for the engine water pump is Aisin WPT-190. And from my notes:

    Engine water pump:
    Toyota p/n: 161A0-29015
    gasket p/n: 16291-37020
    Inverter water pump:
    Toyota p/n: G9040-47090

    This thread, pinned at top of this forum, has very helpful/informative videos (by @NutzAboutBolts), on most everything gen 3:

    Nutz About Bolts Prius Maintenance Videos | PriusChat

    Coolant changes (both inverter and engine) are included. The one exception I'd take with the engine coolant change: Toyota advises to let the new coolant level settle, keep topping up, and when it's stabile, fill to the "B" line, and install the cap. Then proceed with protracted running in maintenance mode. I did this, and the inverter coolant, a few days back, both for the second time. One clue I found to sufficient warm up: I thought it was done, crawled back under to start replacing the under panel, felt the two large hoses running to radiator under there, and they were still stone cold. I put it back into maintenance mode (allows car to run engine continuously), and just lay under there, checking those hoses, till they both got toasty.

    The coolant changes instruction from repair manual attached, plus a few others. Anything you think of, just ask. :).
     

    Attached Files:

    #5 Mendel Leisk, Oct 20, 2025 at 9:04 PM
    Last edited: Oct 20, 2025 at 9:19 PM
  6. PriusTech

    PriusTech Member

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