Noisy rear at high speed

Technical Area Engine, Transmission, Exhaust etc
1
  1. My model of MX-5 is: 2.0 MX5 2006
  2. I’m based near: Oxford
  3. I’m looking for technical help or recommendations on: Diagnose a noise coming from rear of car

I have noticed in the last couple months a higher than usual noise coming from the back of the car. It seems to me that is slowly getting worse (I have noticed because of the radio volume that needs to be higher and higher for me to listen to music).
The noise is speed related. I can start to hear it at 25-30 mph and gets noisier the higher the speed. The noise is clearly coming from the back of the car.
I raised the car to try and understand where this noise comes from and I suspect it is from the differential.
To try and diagnose better the issue, I completed an oil change yesterday and I have noticed some residues catched by the drain plug. The bigger residues are 2mm long and thin flakes of metal, so they are relatively big (of course I forgot to take photos :upside_down_face: ).
The oil change did not have any sensible impact on the noise.

While my suspicion is on the differential, I can’t exclude other components, so I’m open to other ideas
Do you have any suggestion on what could I do to complete the diagnosis?

Thanks!

2

Yes probably the diff, another just like this earlier in the week. First check wheel bearings in the vane hope its that.

Normally you will get a creamy grey paste on the magnetic diff plug, thats ok. If it bits of metal, then something is breaking down. Bummer.

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