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.

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  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
     
    #1 drees, Dec 20, 2021
  2. JC91006

    JC91006 Senior Member

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    most likely bad wheel bearing
     
    #2 JC91006, Dec 20, 2021
  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?
     
    #3 drees, Dec 20, 2021
  4. bisco

    bisco cookie crumbler

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    just keep driving, it should get worse
     
    #4 bisco, Dec 20, 2021
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  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?
     
    #5 drees, Mar 7, 2022
  6. bisco

    bisco cookie crumbler

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    can you record it with the engine off?
     
    #6 bisco, Mar 7, 2022
  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.
     
    #8 drees, Mar 7, 2022
  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
     
    #9 JC91006, Mar 7, 2022
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