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What sounds like wheel bearing failure but isn't?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by jimolson, Apr 20, 2018.

  1. jimolson

    jimolson Member

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    2006 Prius, 160K miles, transmission fluid & wheel bearings preemptively replaced at 150K.

    I've owned 4 Gen II Prii. All experienced wheel bearing failures before 150K miles. Wheel bearing failure sounds like a growl/rumble noise at low speeds and changes frequency with speed. Changing the position of the steering wheel will modulate the rumbling sound.

    Today's sound isn't wheel bearings, although the pitch changes with road speed. At 50mph it sounds like a steady humming/whirring sound from the front end, centered equally between the wheels.

    Normally I would have guessed that worn front tires acquired ridges on the treads but these tires are brand new.

    Is this humming sound indicative of transaxle failure? Any way to diagnose transaxle problems before it fails? I have no MIL codes.

    Jim/Indianapolis, IN US
     
  2. bisco

    bisco cookie crumbler

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    cv joint? did it make the noise before you replaced the tires?
     
    goldfinger likes this.
  3. ChapmanF

    ChapmanF Senior Member

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    You can try to distinguish by the pitch of the sound, with some details here, here, and here.

    Keep in mind that the details depend on the bearing construction (and on the transaxle MG rotor construction, if that's one of the possibilities you're trying to eliminate), and those posts were about a Gen 1 Prius.

    -Chap
     
  4. Lucifer

    Lucifer Senior Member

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    Its possible that one of the new wheel bearings is bad.
    What sounds like bad wheel bearings? Pebbles in a dryer.

    Anyway, after a drive, feeling the hubs would ascertain if one of the bearings was hot, friction.
     
  5. ChapmanF

    ChapmanF Senior Member

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    When my gen 1 had a bad front bearing, it actually measured slightly cooler than the rest. And it didn't sound like pebbles in a blender, more like a distant Cessna. There's such a variety of ways for bearings to fail that sure-fire ways to diagnose them are surprisingly hard to come by. A ChassisEar was the only thing that could finally do the trick in my case.

    -Chap
     
  6. Kevin_Denver

    Kevin_Denver Active Member

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    Based on what you've said, I would not immediately rule out it being a wheel bearing. There are different ways the bearings can fail and cause noise; it may not have failed in the same way as your previous bearings. It can be difficult to isolate sound coming from under the hood while driving. It's probably not wheel bearings based on your experience, but it's worth doing the other wheel bearing checks before ruling it out.

    That being said, if one of the CV joints near the transaxle is failing, it could also cause a similar noise. I would inspect all (4?) CV joints in the front. A failure in the transaxle itself could cause a noise, but I think this is less likely.
     
  7. goldfinger

    goldfinger Active Member

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    You'll know soon enough what it is.
     
  8. ChapmanF

    ChapmanF Senior Member

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    My front wheel bearing kept me guessing for weeks. It was definitely long enough for me to try everything else I could think of, inconclusively, shop around for a ChassisEar, order one, wait for it to show up, then finally figure it out. The sound grew a bit in loudness over that time, but never enough to make the source obvious. When I had the temperature idea I was sure I would find it, but then (as mentioned earlier) I got the coolest reading on the one that turned out to be bad!

    On the bright side, if it's a front bearing, because of the axle nut and way the hub's constructed, I doubt that it's likely to shed the wheel. That's probably a concern mostly if a rear bearing is neglected too long.

    -Chap