Q: Why my car makes metal knocking sound every time I accelerate, and it gone when I release acceleration pedal? It happens at 25+mph

asked by on July 20, 2017

Why my car makes metal knocking sound every time I accelerate the speed, and it gone when I release acceleration pedal? It happens at speed of 25 mph and up. Recently, the noise is louder. The noise keep coming as long as I keep foot on and maintaining the same speed at 25 mph or higher. I can feel the knocking force by my left foot. Specifically, I feel the noise comes underneath of my car from the driver side. That noise is louder when I go straight than when I steer the wheel. I'm not sure what is that sound, and where is it from. Please help me identifying that sound.

My car has 229000 miles.
My car has an automatic transmission.

What you are describing sounds like a failing CV joint. A CV (Constant Velocity) joint is a shaft that connects the transmission to the wheels, essentially transferring the power from the drive train directly to the wheels. The CV joint is packed with a special grease and sealed tight with the rubber or plastic boot, that is held in place with two clamps. The most common problem with the CV joints is when the protective boot cracks or gets damaged. Once this happens, the grease comes out and moisture and dirt get in, causing the CV joint to wear faster and eventually fail due to lack of lubrication and corrosion. When the CV joint becomes damaged or worn, you may hear a clicking, clunking or popping sound coming from this area as the weight of the vehicle puts pressure on this area and shifts back and forth and side to side. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

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