My 240 started making this infuriating noise just yesterday, so I'm resorting to you folks for feedback. It is a whining noise, much like a slipping belt, only upon closer inspection I found it comes either from the rear part of the engine or the transmission (automatic), not the pulleys. Also, it'll only do it when I come to a stop (say, sitting at a red light) and the transmission is engaged. If I shift to park or neutral, it goes away. I did find a few posts describing a whining noise coming from the driveshaft, but they all said it would whine when accelerating, not idling.