The car is an 11 year old Renault Clio.There is no unusual sound if I rev the engine while stationary,but when the car is in motion,there is a heavy drone sound which rises and falls with gear changing and acceleration/deceleration.It seems to me that the car body is amplifying the gearbox in some way but I don't really know?

Rory, August 2009

Its either a noise from the differential bearings or more likely from the front wheel bearings - which are a known Clio issue.

John, August 2009