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Q: My car shakes really bad when going over 40 mph

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My Mazda 3 shakes bad when I'm driving on the fwy. Once going over 40mph, it shakes. Example: if I'm talking out loud while driving over 40, you can hear the shake in my voice. We've checked the tires, had them balanced. And it's still shaking. There's no engine light or anything that shows signs of something's wrong, except before the car was a LITTLE bit quieter than it is now. When we press the accelerator, you hear a slight loudness of the engine vs before, it was a little quieter. Any idea what this could be??

My car has 90000 miles.
My car has an automatic transmission.

Hi there. From the description you have given, your vehicle shakes over 40 mph. The first thought would be the tires like you’ve mentioned. Typically vibration (shakes) are due to something that is out-of-balance. Given the tires and wheels have been balanced, it could be a wheel bearing vibration, as a worn, loose, or bad wheel bearing could cause shaking. It could also explain the noise getting louder as you accelerate.

This could also be an out-of-balance axle shaft, as worn cv joints (attached to each end of the axle shaft) typically creating a clack-clack-clack noise while turning. To get a precise diagnosis, you can get in touch with YourMechanic to inspect the noise in person and follow through with any repairs that are appropriate.

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