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Weird Groaning/Slipping Sound - Acceleration From a Stop When Cold

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by drees, Dec 20, 2021.

  1. drees

    drees Senior Member

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    Have a 2008 Prius with about 150k miles that has started making a funky fairly low pitched groaning slipping sound from the front-left of the car when accelerating from a stop when the car is cold. Only happens when accelerating moderately or more - starts right when the car starts rolling then goes away above 15 mph. Very light acceleration does not make the noise.

    It sounds like what I would expect a slightly grabby CVT transmission might sound like - but obviously that's not the case with the Prius.

    Doesn't seem to be coolant temperature related - if I warm up the engine before driving, the noise still happens.

    Any ideas? Could it be suspension related?

    Closest thing I could find when searching is this:
    Loud noise from ICE when first driving in cool/cold weather. | PriusChat
     
  2. JC91006

    JC91006 Senior Member

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    most likely bad wheel bearing
     
  3. drees

    drees Senior Member

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    Interesting, it could be.

    I did replace the front-left wheel bearing about 6 years ago. Weird thing is that the bearing doesn't make any noise otherwise - why only under load and when cold (keep in mind that "cold" means car has been sitting a while under 60F)?

    Best way to isolate the issue?
     
  4. bisco

    bisco cookie crumbler

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    just keep driving, it should get worse
     
    JahT likes this.
  5. drees

    drees Senior Member

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    So I replaced the wheel bearing and of course, that wasn't it - the car still makes the groaning / slipping sound when accelerating from a stop, until the car is warmed up.

    I'm guessing it has to be the transaxle at this point, unfortunately, which is an expensive repair. Any other ideas?
     
  6. bisco

    bisco cookie crumbler

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    can you record it with the engine off?
     
  7. JC91006

    JC91006 Senior Member

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    Have you tried taking to a shop to see what this could be? Who replaced the front wheel bearing for you? You don't want to keep guessing and replacing parts, it could get expensive.

    I've had a gen2 car with a transaxle problem which is similar to what you're describing at low speeds. It's actually a whining type of noise that I experienced. You would be able to hear it when you accelerate and also when you decelerate (coming to a stop). But you should rule out other things like bad axles, low transaxle fluid, type of problem first.



    If that is the case, then you would probably throw a code when it get bad enough.
     
    #7 JC91006, Mar 7, 2022
    Last edited: Mar 7, 2022
  8. drees

    drees Senior Member

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    It only makes the sound when the engine is running and accelerating from a stop when it's cold. If accelerating very gently, it doesn't make the noise. But I'll try to record it.

    Yeah - bearing was relatively inexpensive and easy to replace, otherwise wouldn't have done it. I think I'll change the transmission fluid for fun as well, though not holding my breath that will fix it, either.

    I was thinking it could be a CV joint/axle, but doesn't seem likely. I have to wonder if it's the transaxle.

    FWIW, if you hold the brake pedal and force the engine to rev, it doesn't cause any noise, which is why I though it could be the hub bearing.
     
  9. JC91006

    JC91006 Senior Member

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    If you hear it when you accelerate and decelerate, 0-15mph, then I would say it's a high likelihood to be transaxle problem. This doesn't necessarily mean it'll fail right away as mine did that for a long time before I replaced the transaxle. If you can DIY a replacement, the cost shouldn't be too high as they are worth practically nothing nowadays. They are thrown away at wrecking yards for taking up space