Quote:
Originally Posted by delta
Picked up a '21 LCI. First M5. I now have just over 2K miles. Enjoying the heck out of it.
But, as I've been getting used to the sounds and operating characteristics that any new ride presents, I've been noticing that when I shut off the ignition, I often get a one-time, audible "clunk" sound coming from the rear of the car. Not a loud nor metallic sound, but one that is definitely audible. Just a dull, summary clunk that I distinctly hear coming from the rear trunk/below trunk area just after pushing the engine start button to shut-off.
Perhaps as important a clue, the sound is accompanied by an abrupt shudder that I can feel through the driver's seat.
The noise and accompanying shudder does not occur every time. When I shut off the car on a level surface, it rarely occurs; but, I've noticed that if I shut off on an incline, or just after driving up an inclined surface to a level surface, and then shut off the ignition, I almost always, if not always, hear that "clunk" and hopefully benign, accompanying shudder.
--Is the "clunk" and accompanying shudder related to some kind of unloading of the M5's M rear axle differential lock?
--Is it some type of lock-up tension suddenly released from the differential at the time of ignition shut-off?
--Possibly an issue with the diffy's lock control unit?
I am not concerned at this point; Perhaps I should...
TIA!
|
Quote:
Originally Posted by delta
Picked up a '21 LCI. First M5. I now have just over 2K miles. Enjoying the heck out of it.
But, as I've been getting used to the sounds and operating characteristics that any new ride presents, I've been noticing that when I shut off the ignition, I often get a one-time, audible "clunk" sound coming from the rear of the car. Not a loud nor metallic sound, but one that is definitely audible. Just a dull, summary clunk that I distinctly hear coming from the rear trunk/below trunk area just after pushing the engine start button to shut-off.
Perhaps as important a clue, the sound is accompanied by an abrupt shudder that I can feel through the driver's seat.
The noise and accompanying shudder does not occur every time. When I shut off the car on a level surface, it rarely occurs; but, I've noticed that if I shut off on an incline, or just after driving up an inclined surface to a level surface, and then shut off the ignition, I almost always, if not always, hear that "clunk" and hopefully benign, accompanying shudder.
--Is the "clunk" and accompanying shudder related to some kind of unloading of the M5's M rear axle differential lock?
--Is it some type of lock-up tension suddenly released from the differential at the time of ignition shut-off?
--Possibly an issue with the diffy's lock control unit?
I am not concerned at this point; Perhaps I should...
TIA!
|
In all honesty it could just be the car shutting down. The new M cars and frankly all new BMWs shutter a lot. Even my 2021 750i does in sport mode.
For our M5s, mine also being a 2021, If you put the car in it's sportiest settings and tap the throttle just a tiny bit, the entire car shutters.
The same effect happens when the fuel is cut off when you shut it down.
This was also relevant in my 2019 comp.
I know it seems weird but it really is normal.