Sound coming from driveshaft

Hi there, my car has developed this nasty sound when accelerating. It sounds a bit like a diesel engine up to about 20 MPH until the sound disappears. All the CV joints were replaced about 1 year ago but im worried the circlip might have come off the end of the driveshaft and is rattling around inside the joint.Is this possible ? The sound must be from the running gear as it only starts when the car moves. Also im getting quite a bit of gearbox growl when i release the accelerator. Any ideas on that one ? Have replaced gearbox fluid recently. Many thanks