On a recent return trip, a loud piercing high-pitched noise started when my speed was 60-65 mph. During the outbound trip, there was no noise and I drove in the 60-65 mph range. At 55 mph or less, the noise was gone. It sounded metallic, but am unsure. During the noise, all the gauges were in normal operating range. And it seemed to be coming from the engine compartment. I'm driving a recently purchased 2002 Winnebago Itasca Suncruiser with 8.1L engine and less than 30,000 miles. Any constructive...