Hello, Am new here and wonder if anyone can help. My 2007 Prius with 44k miles has developed a little whining noise when I slightly lift off the accelerator doing about 50-60 mph. If I accelerate slightly, the whine seems to disappear. Any thoughts??
Regenerative braking. When you lift off the accelerator, you cause a small amount of regenerative braking, which is done by MG2. That makes a whining sound. Tom
Thanks, Tom for the reply. Don't think that's what it is since this is a new noise and has not happened in the past. It seems to happen only when I'm going 50-60 mph and lift off the accelerator slightly and depress accelerator again.
The inverter pump on mine died last week. Since it was replaced, for the first time in five years there has been no inverter whine. I wonder whether the inverter was chronically starved of coolant all that time?
We also have this whining noise. The car has 103,000 miles on it and it has gotten alarmingly noticeable, almost loud at 60-65mph under very light load. With foot off the accelerator, it goes away; under heavy load it almost disappears. It's most noticeable under light load, just as one would expect if the pinion bearing play (or whatever this transmission has) had increased. It's not regenerative braking; it's not an electronic noise. It's not coming from the power split device. It's in the final drive gear, probably at the differential. The pitch is proportional to vehicle speed, not engine speed. We took the car to the dealership just before the 100k extended warranty ran out and they said "no problem. In the 4,000 miles since then I think it has gotten louder. Transmission oil was changed at about 95k.
Light load tends to suggest what you have said. Also remember that MG2's speed is proportional to vehicle speed, since it is directly connected to the drive system after the PSD. Any inverter or mechanical noise related to MG2 would show the same speed correlation. Given your mileage, I'm guessing mechanical noise, but that's only a guess. Tom
