CHRVM2YD

Hi all - new to this forum. Recently bought a pre-facelift S63 coupe and started to notice a high-pitch whining noise coming from the rear of the car.

From what i noticed:

• The whining noise is high pitched, almsot feels as if there is a moped trailing behind me
• The noise only comes on after 10-15min of driving
• I think the noise is more noticable at lower speed - most prominent when the car is slowing down (e.g. when you feather the throttle, you hear the noise more when you lift off the pedal)
  • Maybe at higher speed the noise is just drowned out by the engine sound?
• It also becomes more pronoucned after flooring the pedal and traction control comes into effect
• Soemtimes when i drive over bumps i feel the car loses grip for a fraction of a second
• I can also hear the noise even when the car is stopped with engine on idle
• I can only hear the noise from the inside - cannot hear anythign from the outside (of course without having the car lifted on a ramp)

Had my engien and transmission serviced and the noise still persists. Doing my own research feels like this could be the rear diff. If it was the wheel bearing, the noise should be more prominent at higher speed / should not have been a noise at a standstill right?

Be great to hear your opinions too!

Many thanks in advnace