My 300SD has a 'whirring' noise (fairly low pitched) while I press on the pedal. It changes pitch as the RPM's go higher. The 300SD sounds like a jet engine (or race car) when I'm accelerating. If I let off the gas at all, the noise immediately stops, irrelevant of RPM's or driving speed. It almost seems like whatever this noise is, it's coming from the vicinity of the torque converter.

Is this indicative of a problem? Perhaps time to change transmission filter/fluid?

Or is this an indication of something in the transmission or engine worn out?

The whirring noise on the car actually sounds kinda cool. My 300TD wagon sounds differently (more like a rattling tank than a jet engine), so I'm not sure if there's an issue.