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Mazda low speed thump

I have a 2006 automatic Mazda3 2.3 sedan with 41,000 miles. I’ve noticed at speeds near 20-30 mph if I’m coasting and then lightly press the accelerator to keep speed there is a audible clunk/thump that I can feel before power is delivered to the wheels. It feels like something is either shifting in place or engaging real hard. When I release the pedal it thumps again, just not as hard. It seems to happen mostly in third gear. I have no harsh shifts.



I’ve had it in to the dealer, and they replaced my motor mounts and transmission mount. The problem is still there. Any thoughts? Could it be bad transmission fluid?



Thanks

“Could it be bad transmission fluid?”

Maybe yes, maybe no.

However, since the car is now at least 3 years old with 41k on the odometer, it is overdue for a trans fluid change. Anyone who wants to keep his/her transmission operating properly for the long term should be sure to change the fluid (and filter, if so equipped) every 3 years/30k miles (whichever comes first). In the case of Mazdas, which have a history of “weak” transmissions, it is especially important.

This may not resolve the problem, but it is definitely a good place to start.

Just be sure to have a fluid change performed, NOT a fluid flush. And, whatever you do, DO NOT go to AAMCO, Lee Myles, Cottman, or any other chain transmission operation. Go to an independent trans shop that has been in business for at least 3 years.