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Thread: MMH Noise?

  1. #1
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    MMH Noise?

    I just got my MMH about a week ago. (I am getting about 32mpg overall btw). I do notice that on the interstate and at high speed in general, there is a very noticeable whining noise. At first I thought it was feedback from the sound system, as I have had this in other vehicles from a bad ground or something. Surely it has something to do with the electric drive. Does anyone else hear anything?!?

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  3. #2
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    Quote Originally Posted by jdnels View Post
    I just got my MMH about a week ago. (I am getting about 32mpg overall btw). I do notice that on the interstate and at high speed in general, there is a very noticeable whining noise. At first I thought it was feedback from the sound system, as I have had this in other vehicles from a bad ground or something. Surely it has something to do with the electric drive. Does anyone else hear anything?!?
    The electric drive motors would be the last thing I would suspect unless the eCVT is low on fluid. Some things I would look at is does the sound increase or decrease with speed, which may be a drivetrain or tire problem. Does the sound change with RPM which may be associated with electrical feedback. The FEH/MMH will have high RPMs during acceleration which is normal engine noise, so let off the gas to see if it goes away. How does acceleration and deceleration effect the sound?

    I need some additional information in order to help you out here.

    GaryG

    Try a neutral coasting test when the sound is heard to separate the engine and eCVT from the axle and drivetrain.

  4. #3
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    I really don't notice the noise at lower speeds. I will say it is independent of rpm and does not matter if I am accelerating or not. when watching the HEV display it is clear that the noise occurs when the electric drive is 'energized'. Specifically, when the ICE appears to be running the electric motor as seen on the screen. I just called the dealer and they said the noise is normal, but doesn't seem possible. thanks!

  5. #4
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    Quote Originally Posted by jdnels View Post
    I really don't notice the noise at lower speeds. I will say it is independent of rpm and does not matter if I am accelerating or not. when watching the HEV display it is clear that the noise occurs when the electric drive is 'energized'. Specifically, when the ICE appears to be running the electric motor as seen on the screen. I just called the dealer and they said the noise is normal, but doesn't seem possible. thanks!
    You can hear a change in my FEH when the small generator begins to charge, but it is only a little change in sound only at an idle while at a stop.

    The small generator can recharge the HV battery in neutral above 6mph, but all regenerative charging from the traction motor is removed. I suggest you test to see if the sound is present when the battery is full and there are no charging arrows to the battery while the engine is running at a speed you normally hear the sound. If the sound only comes back when the small generator arrow goes to the battery, there may be a problem. In addition, shift to neutral above 6mph to eliminate the traction motor charging or other drivetrain noise to see if the noise is still present from the small generator and engine.

    If you determine the noise is only present between the engine and small generator, you may have narrowed down the problem location. There are many sources that can cause noise between the generator and the engine, but I need to get to this point to go further. It could be the one-way clutch got contaminated with oil or grease during assembly or a problem with the generator brake and clutch assembly. There is also a self adjustable engine/transaxle mount that is designed to reduce vibration and noise that may have a problem. If the noise is not normal and coming from the eCVT, there is no repair other than reflashing the Transmission Control Module that can be made. This means the eCVT must be replaced and that would be the first time I've ever heard of a replacement. They will have to remove the engine and eCVT as a unit to replace the eCVT FYI.

    My bet it is not the eCVT based on the reliability so far. If anything, it may be from damaged shielded wiring, or other drivetrain noise.

    Good Luck, and let us know.

    GaryG

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