High pitch noise query F80 M4 comp

[Chazzmania]

Hi all,

Noticed a strange noise recently which I'm finding difficult to describe but here goes:

Usually occurs after pressing accelerating for a short period of time and then releasing it, sounds like a high pitched whir or almost hydraulic noise, only a very short sharp noise (not constant) and can sometimes occur twice in a row after releasing the accelerator. I also noticed a similar/same noise immediately after pressing the accelerator also. This all occurs at relatively low speeds - 20-40mph, think town/city driving where you're on and off the gas pedal due to fluctuations in traffic flow.

Anything to be worried about? Any help ish greatly appreciated.

[t5pilot]

Check your diff seals. Mine's been making a similar noise recently. Oils misting was an advisory on my recent MOT.
Couple of weeks ago found a small drip amount of diff oil on my garage floor. Nothing since then, but it's obviously seeping. Coupled with the strange noise occasionally.
Better safe than sorry, got mine booked in at the end of March for both n/s & o/s diff seals replacing, along with new diff oil & KDS alignment afterwards.
I'm sucking up some cost now, which is small in comparison to the diff having to be replaced if I just leave it.
For perspective, my car's May 2017 with 31K miles. Was a pre-reg, so no previous owners other than BMW.