I'd posted previously about a whine/screech sound that my '08 MMH makes at certain speeds. I've now confirmed that it happens only when in gear, and only at about 25-35 and 55-65 mph. Shifting to neutral, the sound instantly goes away. The sound is there when accelerating, braking or coasting at those speeds (but it instantly responds to pressing or letting off the accelerator). It's worse when the car is fully warmed up and has been driving for some time.

The sound is a metallic whine or screech - like a bad bearing or the whine from electric interference, and seems to be coming from the lower middle to front of the car. It's completely different from the whine of the electric motor, which the 07 FEH I'm familiar with makes - this is a different noise.

Any ideas what this is?

Now that I can isolate it, I'm going to take it to the dealer when the car is warmed up and see if they can have a tech sit in the car and listen to it (they said they couldn't reproduce it when I dropped it off last month).

All ideas welcomed...

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2008 Mercury Mariner Hybrid 4WD
1999 Mercedes E300 Turbodiesel