Okay, so I have a 2006 F250 4x4 Crew Cab, 6.0L, all bone stock except for a SCT Tuner for EGR delete. I found it a few months ago from an old guy who kept it in his garage with 24,000 orig miles. It is pristine. So this past weekend I towed my 9000lb 5th wheel, (10k loaded), a few hundered miles. Sometimes while towing, usually uphill but sometimes on flat ground, always while under some power, I can hear a fairly loud sound, not accociated with the engine. It sounds like maybe the tranny slipping, but the rpm's never change and it doesn't alter or effect it's preformance. It sounds like a smooth engine reving up then coming back down, normally not lasting more that 5-8 seconds. It almost sounds like a fan or cooling device too. The truck is in the tow mode when this happens. The tranny temp doesn't change and no warning lights come on.

Is this a normal sound? If so, what is it? If not, whatcha think?

My other truck is a Dodge 2500 4x4 Hemi, but never made this sound.

Thx for ANY advice.

Dan

 

Sounds like your fan clutch engaging. Perfectly normal. Especially while towing.

 

Sounds like the cooling fan... VERY loud on these trucks

 

It's the engine fan, it'll come on based on a number of parameters. If you put gauges on the truck you can read the actual coolant, oil, and trans temps right out of the OBDII port:
ScanGauge II Ultra Compact 3-in-1 Automotive Computer with Customizable Real-Time Fuel Economy Digital Gauges : Amazon.com : Automotive

 

Thx for the advice. Set my mind at ease. I'm going to order that gauge display today. Thx again!

 

You can display fan speed with that gauge too. See if it increases when your noise happens. The fan is very big and computer controlled on the 6.0. All my friends joke that it sounds like a c-130 plane taking off, lol.

 

my 5.4 does it to, never thought thats what it could be. always wonderd though