Knocking Sound At Low RPM at Low Speeds

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Feb 13, 2026 | 09:06 PM
  #1  
HI everyone,

I recently bought a 2015 GLK350 RWD with 81k miles. It drives great and looks great. I do noticed that the car has a knocking? sound at low speed low rpm when accelerating, and when its not warmed up gives a slight vibration too with the knocking sound. I found a very video showing a very similar sound in reddit. Does anyone have an idea what the sound might be? I checked the timing chain on cold start but don't hear any rattle when starting. Also, the engine mount was replaced by old owner. If anyone could give me any ideas what to look at, it would be great. Thanks in advance.

Video Link: https://www.reddit.com/r/mercedes/co...0_weird_noise/
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Feb 14, 2026 | 07:44 AM
  #2  
Any idea where the sound is coming from? Engine? Transmission? Driveshaft?
if it’s only when moving, I would look closely at the driveshaft and half-shafts. CV joints can make noises like that at low speeds when they fail. I would inspect the CV boots for cracks/tears, and look for evidence of grease outside of the boots.
Unfortunately there are a number of things that can cause knocks and clunks. If you have an automotive stethoscope ($10 at HF), it can greatly help find sources of odd noises.
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