Ok, I've seen this question asked a couple of times, but not with enough info to fully describe it so it could be answered. I have an 89 240 DL. A couple days ago it started making a strange whining noise when running at 50 mph and above. It is not a grinding noise like a bearing or brake pad. It is not the hum from a fuel pump issue. It is not the squeal of a belt slipping. It is more like an electric whine that comes from the front of the passenger side. Upon hitting 50 mph it starts like a small electric motor spinning up to high rpms until it gets to a steady high pitched whine. Then if I let off the gas, it sounds like it is spinning down. My wife compares it to the sound of a tiny jet landing when decelerating. When I try revving the engine, while parked, to an equivalent rmp I do not get the sound. I'm sure it's not the fuel pumps because I've just replaced both and am very familiar with the pump noise. I'm also familiar with belt squeals, brakes grinding and bearing noise and that's not the type of noise I'm hearing. This is stumping me so any help will be appreciated.