Hey guys just started having this engine reving sound coming from the truck while driving down the highway, running ac, sounded like engine rpms were just tacking out but the rpms don't move. Sound continues a moment or two and then whines back down. Does anybody know if this is transmission or something else. Oh I am towing a cargo trailer this is a 450 2001 7.3 bucket truck.

 

Sounds like normal operation of the fan clutch.

 

^^^ I second that motion...

 

And third..........

I heard the fan a LOT yesterday towing the camper.

 

^^^^^^^ What they said!!!

 

.... and fifth...

Sounds kind of like a jet engine spooling up, doesn't it?

 

........... And I will "sixth" that.

 

Yes it sounds like a jet engine taking off. Then it sort of comes to a landing and sound goes away. So this is normal or is something loose? The fan does not wobble. And belts are almost new. Should I just ignore it???? Thanks for all the input...

 

It should make that sound until the fan clutch wears out.... That is the sound of the fan MOVING air...

 

yes its suposed to do that, every thing is fine. ignore it..

 

Our you towing when this happens? How hot is the motor? Dose the gauge move at all? Sounds normal but what are you doing with the truck when this happens? Could be a start of a plugged radiator causing this also if your not working the truck hard. Or thermostatic.

 

As most others have said - fan engaging and doing its job.

I tend to hear mine a lot just slowing to under about 35 then having to accelerate again (reduced airflow) when towing or especially in stop and go on a hot day.

If your truck is pretty normal, you probably will hear it roar on first start of the day for the first 1/4 mile or so, even in cooler temps.