Hey everyone,

I'm having a bit of an issue with my 2011 S550 W221. I've noticed a knocking noise coming from underneath the car, specifically around the front seats. It seems to happen when I accelerate, decelerate, and sometimes (not all the time) even when coming to a complete stop.

The noise is quite noticeable and a bit concerning. I'm wondering if anyone else has experienced something similar or has any ideas on what might be causing the noise.

Any advice or suggestions would be greatly appreciated!

Thanks in advance,

suspension bushes fall apart and ball joints wear - but the ARB (anti-roll bar) bushes get stiff and shrink back allowing the ARB to rattle in the main bushes - making a nasty noise as you slow or pull away (most noticeable in slow moving traffic - you can feel it through the pedals too) if its this u can live with it without issue it doesn't cause harm, just sounds and feels awful

Thanks for your feedback. It does not sound like a suspension issue. It is a knock when I push or release the gas pedal. It sounds like a drive shaft or transmission issue but, I am not sure. I was wondering if anyone else has experienced the same thing. It only knocks once when I push the gas and once when I release. It does not rattle or squeak.

Sounds like collapsed transmission and/or motor mounts.

If you have a 4MATIC it could be the front driveshaft failing due to the u-joint. It happened to me and I had those rapping noises.