Gearbox grinding after hard drive

[PV]

Hello

I have had the M5 for about 9 months, no problem other than the squeaky brakes.

Then the other day after driving it hard when I came into town and slowed down the gearbox was making an extremely loud grinding noise, sounded like spinning metal discs grinding together.

No warning messages were displayed and did not affect the way it drove at all.

Seems to be running fine now, no noise since.

Any ideas?

Thanks
PV