E30 320i gearbox noise

[Dolphin]

Hi The 320i has developed a fairly loud scraping sound from the gearbox. The sound is present in all gears and when the vehicle is coasting in neutral. There is no sound when the car is stationary.
Sometimes when driving there is a whir followed by a clonk and the sound goes away for a while. Ant ideas?

Cheers

[Brianmoooore]

Guibo between the box and prop shaft breaking up and flailing against the underside? 'Clonk' when a bit breaks completely off.