I have a 1989 740 turbo. It just started making the weirdest sound. When the car is cold, getting up to speed it starts to whine. It's a high pitched sound, almost like a siren. The sound does not fluctuate with the engine RPM's. When driving, I can put the car in neutral, and the pitch of the sound is no different. It sounds like it's coming from the right side, possible rear of the car. The sound goes away after about a 1/2 mile of driving. Speaking of driving, this is driving me crazy. I checked the turbo, that's fine. I replaced the rear brake pads, no difference. Transmission fluid and differential fluid are fine. Any ideas?