2000 Toyota Prius • 4 cylinder 2WD Automatic • 98,000 miles

My 2000 Toyota Prius has made a noise for the last three months which sounds like the engine is working harder or like tyre noise. The noise does not go away when the engine is put into neutral. The noise hasn't got any worse over this time and there are no performance problems. I am not sure whether the transaxle oil should have been topped up or changed?
Please let me know what you think.

John O'Brien
March 4, 2011.

Check trans fluid, check wheel bearings, and check transmission output shaft bearings.