1999 A3 (AGU engine)

I have a constant (fairly loud) rotational, knocking noise develop when driving off throttle, breathe on the throttle and its disappears!

Jacked car up and looked over the suspension, driveshafts, wheel bearings and it all seems fine. Only way to replicate noise was by spinning road wheels, seems there is some free play in the gearbox/diff as you rock/spin wheels?

Gearbox knackered?