Hi all!

I've been a guest here for a very long time and find the forum a very valuable source of information for Porsche. Since something unusual started to happen to my car lately I decided to register and ask you guys. Maybe a similar thing happened to any of you.

The problem:

The vehicle emits a strange grinding sound with a tone that changes depending on engine RPM and the car speed.

For example, you can hear high-frequency sound when decelerating and going through ~15mph.
You'll hear the constant sound when driving 60mph and maintaining the speed.
When driving ~30mph with low RPM/5 gear you may hear a low freq sound with a bit of 'buzz'.

I was able to record the sound. The conditions were: approaching 60mph slowly and maintain it for a moment, then reduce gear to 3rd (at the end) where higher frequency is heard.

What was done already:

The car had the engine rebuilt last year (often 3.8l case).

Differential was regenerated with new parts and oil.

Ideas:

I thought it may be a wheel bearing causing this, but the sound doesn't match this. I was also performing a few test rides with turns to check this.

Oil/water pump? The only thing related to the oil pump that comes to my mind is that the pressure is not full when the engine is warm. It reaches 5 when cold but as soon as the temperature of the oil is established it won't go higher than 4.2-4.5 / 5 even with full throttle and high speed.

And this way... I run out of ideas.

Have a good day everyone!
Mateusz