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When trying to determine the source of vibrations at idle in my 98 Mazda 626 GF 2L one thing I've found mentioned by many people is a potentially worn out / failing torque converter. However, when researching the matter in the relevant Mazda workshop manual and in the ATSG manual for this specific transmission, neither one of them mention vibrations as a symptom of torque converter problems. However, they both mention excessive noise from the transmission while idling as a potential symptom of such problems.

The closest conditions mentioned in the ATSG manual are:

  • Noise severe under acceleration OR deceleration, OK in park, neutral or steady speed
  • Noise in Park or Neutral - does not stop in Drive

It's similar in the WSM, but vibrations aren't mentioned anywhere.

So are vibrations, without noise a potential symptom of torque converter problems and of course, if so why?

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I'm not a TC guru, so I'll refer you to this question for the different failure modes. What I can provide is the engineering theory behind vibration.

Any rotating mass will suffer from vibration if there is a rotary mass imbalance about the axis of rotation. If you have a table fan, try to tape a coin to one of the blades and you should be able to visibly notice the vibrations when the fan turns on. This is also the reason why wheels have to be balanced with weights.

So if a torque converter experiences some type of failure that results in rotary imbalance (a failed weld or chipped blade come to mind), the vibrations in the drivetrain may be bad enough that you can feel them.

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