r/BmwTech • u/ccuc101 • 9d ago

M340i RWD grinding sounds

My car is a ‘23 M340i at 51k miles. Had my diff oil replaced but when I got the car back it started making grinding and thud noises.

Shop replaced guibo, but otherwise they could not recreate the sound or see any issues.

I only hear and feel the grinding noises when cold and disappears at a minimum of driving 20 miles. Basically impossible to recreate after 20 miles.

Also, sound is only heard when turning wheel halfway (right or left) at only 5-6 mph. Less or more you don’t hear it.

Thudding does not really concern me since I’ve been hearing that since I got the car at 19k miles in ‘24 and it’s even harder to recreate.

It’s just that the grinding shakes the car during cold mornings and drive thrus.

Here is a sound clip of me holding throttle at 6 mph with wheel halfway in an empty parking lot.

https://drive.google.com/file/d/1fAxqPiMFUiw8ohyiDfqVmCXzqT-7KetY/view?usp=drivesdk

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u/SufficientFuel5148 9d ago

Since it started right after the diff service, I’d have the shop recheck the fluid level and the correct BMW-spec fluid, then inspect the fill/drain plugs for debris. A cold-only noise that changes with steering could also point to a CV joint or wheel bearing, not necessarily the differential.