1986 VW Cabriolet Rabbit convertible-- drive train question



i have a BEAUTIFUL 1986 VW cabriolet convertible. i have recently started to hear a knocking/scraping noise when i am either 1) not in gear, coasting, or 2) in (any) gear, not accelerating. this noise stops when the car stops. my mechanic seems to think it might be an axle issue or maybe even a transmission problem (hoping it’s not the latter). i don’t think it’s a tranny problem because it makes the noise even when the tranny isn’t engaged (in neutral, coasting). anyone have any ideas?