noise in reverse

Discussion in 'Gen 4 Prius Main Forum' started by Dennis Palmer, Jul 9, 2022.

  1. Dennis Palmer

    Dennis Palmer Junior Member

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    My 2020 Prius make a grinding sound when backing up. Can only hear it out side the vehicle. At first thought it was brake pads making noise. thought it would go away but 10000 miles later it is still there. Asked at the dealer and they said it was designed this was so that people knew the car was moving. Is this BullS**t on normal.
     
  2. jdenenberg

    jdenenberg EE Professor

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    Your dealer is talking about the "spaceship" noise that is generated at low speeds in either direction. Does the "grinding noise" only occur when you engage the brakes? If so it is rust on the rotors and you can clean them by getting up to 25-30 MPH, putting your Prius in neutral (to shut off regenerative braking), and applying the brakes lightly. Repeat as required to eliminate the noise/rust.

    JeffD
     
  3. BiomedO1

    BiomedO1 Active Member

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    I'm pretty sure it's normal. Mine only happens in reverse, and it's not a grinding. It's more like a wet finger on crystal drone or a bad wheel bearing sound (if you've ever experienced that). You probably only noticed this, once you've turned-off that incessant reverse beeper and you have your windows rolled down.
    If you had a real problem, the grinding sound would persist - moving forward or back. Since your issue is isolated to reverse, I doubt you have a problem. If you think I'm full of BS - Find someone else with a Prius and have them throw it in reverse. Unless they modified or clipped that external buzzer; It should sound similar.

    Good Luck......

    PS. It needs to be a 2017 or newer Prius. The older ones had something similar, but they sounded way different.
     
  4. Jburner

    Jburner Junior Member

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    It's actually a speaker in the front. They had to add the speaker to make a noise when the car was moving for safety reasons.
     
  5. bisco

    bisco cookie crumbler

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    ifit were the VPNS, it would make the same same forward or backward up to 15mph or so.

    open the drivers window and listen in both directions with the engine off.

    Electric_vehicle_warning_sounds
     
  6. Dennis Palmer

    Dennis Palmer Junior Member

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    Do you know where the speaker is located? Or at least close to where it is located
     
  7. bisco

    bisco cookie crumbler

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    somewhere in the engine bay, there's at least one thread here somewhere
     
  8. bisco

    bisco cookie crumbler

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  9. A strolling player

    A strolling player Junior Member

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    It’s not only on in reverse, it also sounds in drive when the gas engine is off up to 22 mph. It’s much louder in reverse so people behind the car can hear the sound, because the speaker is up front.
     
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  10. bisco

    bisco cookie crumbler

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    that's interesting, i had not read that before. makes sense though
     
  11. BiomedO1

    BiomedO1 Active Member

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    LoL; I'm getting old and my hearing is going anyways. I had a service call today about an incessant hum - I couldn't hear it. So I unplugged the monitor, and she said it was still there. I unplugged the UPS, and she goes - it's gone, but can you do something about the alarm?:p:D:cool:
    So I asked her, which is more annoying - the alarm or the hum. She says, well the alarm. Great!!! another satisfied customer!!!!:D
    Actually, I told her it'll take me about a week to get you a new UPS.:whistle::ROFLMAO::LOL::cool:
     
    #11 BiomedO1, Jul 12, 2022
    Last edited: Jul 12, 2022
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  12. Media_Tech

    Media_Tech Junior Member

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    Maybe the clutch? IIRC it need to disengage the drive train from the ICE for the car to be able to go backwards.
     
  13. jdenenberg

    jdenenberg EE Professor

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    There is no clutch in a Prius (other than a "torque limiter")

    JeffD
     
  14. Media_Tech

    Media_Tech Junior Member

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    John Kelly, WeberAuto:
    2016 - 2022 Prius, Prius Prime Transaxle - P610 Deep Dive (P710, P810 Similar)
    Toyota - YouTube
    starting at about 9 minutes into video.
     
  15. bisco

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  16. Mambo Dave

    Mambo Dave Active Member

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    whoah.

    I must have skipped over that part back when I watched the video. I'm still impressed that two rotors are turning up to 17,000 RPM in there.
     
    #16 Mambo Dave, Jul 15, 2022
    Last edited: Jul 15, 2022
  17. jerrymildred

    jerrymildred Senior Member

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    Yes, new models are MUCH louder in reverse. Different sound, but nearly the same volume as an idling diesel truck. Seriously annoyingly loud.

    As for Professor Kelly, his Prius videos should be required viewing for Prius owners.
     
  18. ChapmanF

    ChapmanF Senior Member

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    A direct link to that P610 deep dive video makes it easier to see what part you're referring to.

    At around 9 minutes, Prof. Kelly starts talking about what he calls the "clutch" damper, as you can see here. JeffD knows about that; it's what JeffD called the "torque limiter". Toyota's parts catalog calls it the transmission input damper assembly.

    tlim.jpg

    If you've looked at clutches before, you can see this looks a lot like a clutch pressure plate and clutch disc permanently assembled together, but with no means of releasing, ever. It has the coil springs that take up brief pulses in shaft torque, and it is able to slip slightly whenever there is torque that would exceed the mechanical limits, but that's all it does. All the rest of the time, it just rotates as one assembly; it does not act in any way as a clutch that can release. Every Prius has one of these.

    A minute or so further into the video, Prof. Kelly discusses (but does not show) an additional "clutch" that only exists in the Prius Prime. The sprag clutch lives between the engine block and flywheel, and is simply a fixed type of one-way clutch that won't let the engine spin backward. It is needed in the Prime because the electric motors can drive the car forward at higher speeds, by pushing off against the engine crankshaft, which therefore has to be held against turning backward.

    sprag.jpg

    So in a Prius Prime, there are two kinds of clutch-like thing, but still nothing that ever disengages the engine from the drivetrain.
     
    #18 ChapmanF, Jul 15, 2022
    Last edited: Jul 15, 2022
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