Whining sound when towing. Trouble?

[SHavis]

When towing serious load with my '01, every 5-10 minutes of so I'll hear what sounds like a whine the increases in pitch, steadies out for a few minutes, then tapers off. There doesn't seem to be any loss in power. No smoke or any other odd behaviors when this happens. It doesn't sound like a fan due to the ramping/unramping of the noise.

Is this right? I've had this truck since new and put 300K miles on it & never heard this until I got an offshore boat to pull.

Should I be conserned?

Thanks!

[coot1]

Rear ends will tend to whine when they are on the way out.

[SHavis]

Originally Posted by coot1

Rear ends will tend to whine when they are on the way out.

It's definately not gear related. It's forward of the passanger compartment. I know gear whine, and this ain't it.

[countryraised]

how much other towing have you done, is it turbo surge? it happens more under more load on the late 7.3s

[SHavis]

Originally Posted by countryraised

how much other towing have you done, is it turbo surge? it happens more under more load on the late 7.3s

Done A LOT of towing. Mostly my FJ40 on a flatbed. The boat weighs a lot more and stands up in the wind, too. If I were guessing, it sounds like exhaust gasses. Certainly could involve the turbo. Could the exhaust temp be getting too hot and the wastgate is opening or closing? Guessing here...

Turbo surge is ratchety, right? This is definately a smooth roaring(like a fan) whine.