One problem related to loud engine noise has been reported for the 2000 Lexus RX300. The most recently reported issues are listed below.
After first having to replace my transmission at 75,000 miles. It seems I will have to pay to do it again at 186,000. The problem started out with the vehicle having trouble climbing a hill. I changed the transmission oil and two weeks later the vehicle move about three feet from a parking stall made a loud noise jerked to a stop and would not move. I was able to put it into drive and repark the car. It will not reverse and had to be towed to a mechanic.