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Does this sound like a transmission issue?

Hello, I’ve got 1999 Kia Sephia with ~130,000. Rebuilt the transmission at ~100,000.

Recently when I would shift it into drive, I would hear a loud noise steady noise, sort of like a muffled Harley running at a red light, the vehicle also vibrates a little. When I accelerate it gets a bit louder. This noise was never usual.

The second I put the car in neutral I can tell the transmission disengages and the sound is no longer made. It never happens in Neutral or Reverse. Is louder during acceleration but when I stop accelerating after 25 mph the car sounds like it normally did.

Also I revved the engine at neutral and it sound just fine.

What do you guys think?

A muffled Harley would be rare.

Well it wouldn’t sound exactly like a Harley, I just cannot imagine any other way to describe it. Maybe a better way to describe the sound of a loud muffler under the hood.


I think your trans needs surgery again.

The check engine light came on today, and I went to have it checked, it was an O2 sensor. The mechanic things is a leak in the exhaust, which would make a lot of sense with the noise sounding the way it does, and the headache I’ve been experiencing.

The leak must have also gotten worse because I can hear the noise most of the time now. I suppose that before when the leak was a lot smaller putting the car from neutral to drive increased the exhaust, I have no idea how that might happen but that would be the only reason why there was a noticeable difference in sound between the two.

Thanks for your replies!