Vibration noise from back of car in 1st & 2nd gear

[Grahd]

I have a Clio Authentique 2002 1.2 8v when in reverse, first and second I get a vibrating sound when accelerating it seems fine if I rev when I'm not in gear and nothing actually vibrates it just has the sound of it. Sounds like it is coming from the exhaust. Any idea what it could be?

It does not sound like the wheel bearings

Thanks if you can help.