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Q: Knocking under car.

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I have a very loud knock that sounds like it's coming from the driver's side wheel well of my car. The odd part is, the knock only happens when the car is rolling and the engine is not braking, turning, or under load. So the knocking doesn't happen when I accelerate, it doesn't happen when I brake, and it doesn't happen when I turn. It doesn't just get quiet, it stops completely. I've checked the u-joint, and both wheel assemblies. I'm at a loss...

My car has 200000 miles.
My car has a manual transmission.

This is may be anything from wheel bearings to ball joints and struts. The fact that it only happens when the car is rolling and not under a load suggests that it may also be something as simple as something being caught in the wheel or axle assembly. Without hearing the sound, further diagnoses would be difficult. I would recommend having an expert from YourMechanic come to your home to listen and test drive to diagnose and repair.

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