Hello my friends !
First of all,I'm sorry for my bad english.

I have a 116i/2004/n45/manual 5 speed gearbox/85kw.The car has now 170k km.
In the last 2k km a weird sound appeared from day to day louder and louder.Now it is very hard not to hear it.
The noise sound like a mettalic creak proportional with the speed.
The sound first appeared only the car is in gear and only deceleration,especially at low speeds when the whoush from the air and engine.I heard it when I accelerate but only as a fine sound like a metallic turbo spool,but when the car decelerates is is very clear.
When I decelerate (in gear (1sh,2nd,etc)) and the sound is heard ,if I press the clutch or put it in neutral and the car decelerates only from the friction with the road-the sound does not appear.So I believe that is a transmission problem.The engine works ok(in gear or neutral-no weird sounds at all).
The read bearings are new.The brakes work perfetly,no sounds.
I have a new flywheel(chaged about 10k km) and last week new clutch kit(3 pieces).i hoped that the sound was from the old clutch-but it seems is is the same.
Last month I changet the read diff oil(Castrol 75w90),the old oil was yellowish ,a little cloudy(14years and 170k-no surprise!) but no metalic residue on the filler cap.After the oil change,the sound was the same.
That is how to car sounds in 1st and 2nd gear when decelerating(in gear)
https://www.youtube.com/watch?v=nH4fL4dSyBw
And a video when I go in reverse slowly rising the clutch pedal until it is full-up.
https://www.youtube.com/watch?v=UHyiTfvHW44
Untill now at the garages that I was I was told :
-the gearbox(a bearing-something..)
-the rear diff
-the driveshaft(bearings/support/joint/etc etc).

Anyways,all of these are quite expensive repairs and I don't know where to start/go.

Please help !