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Same problem here
I am having the exactly the same problem on my 760 Li 2011.
While accelerating around 100 km/h (55 mph) the rumbling/humming noice and vibration is very clear, while coasting in 55 mph it almost disappears completely. At higher speeds I have to press the gas pedal harder in order to get the noice. Coasting in higher speeds = can not hear noice ot feel vibration at all.
The parts I have replaced without solving the problem:
New engine mounts + gearbox mount
New propeller shaft incl 2 x guibo and center bearing
New (used part) final drive
I have used 4 sets of different wheels = problem does not come from wheels or tyres.
Drive shafts are not replaced but they have zero play.
I am 100% sure it has nothing to do with engine or gearbox (also working perfectly)
I have 275/35-20 rear tyres.
In general, the complete drive train of my car was in bad condition when I bought the car. I had a play in the old propeller shaft with a clicking sound, engine mounts were also in bad condition. I think the former owner in Germany used the power a lot in this car...
However, I just discovered that there is a play in the HSR actuator (rear steering). When I try to rock the track rods by hand I can clearly see (and also hear) a play of about 1-2 mm up and down on both sides of the HSR actuator. Also when the tyre is moved by hand i can feel and hear the play.
This means that the mounting points of the track rods possibly could start to vibrate and create noice and vibration in the car?
By pressing the gas pedal the forces on the track rods increases a lot which may explain why the noice comes with acceleration?
Please post answers what you think about my theory and hopefully some of the members in the thread can post if they found the root cause of the problem or if their cars have HSR actuators.
Plaase check enclosed picture with two red circles showing where the play is located. Picture is from below and the front of car is pointing downwards.
Best regards, Tomas
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