Yesterday I was driving through the mountains of TN hauling my 18' box trailer. It was towing just fine but I noticed a noise that I have never heard. The noise sounds like it would be coming from the rear of the engine like near the flywheel area, but I could not pinpoint for sure. It would only do it for a few seconds at a time, but it got me nervous. It almost sounded like an auxiliary fan coming on or something. I have owned the truck since Feb and it has NEVER made that noise. BUT I have also never towed this big trailer loaded through the mountains with the A/C on before yesterday. All temps and fuel pressure looked spot on....
Is there anything to worry about? You guys don't think it could be some sort of bearing going out do you? Truck has just over 56k miles on it.

I would say the Thermostatic Clutch Fan was kicking in.

Brian

X2 on the fan clutch, sounds like a turboprop plane has just wound up under your hood.

Good deal. Thanks guys!

does it only do this under load?

It can also come on when driving in very hot temperatures, typically stop and go kind of stuff.

mine makes a whinning noise when the motoro is cold. sounds like an altenator but is coming from behind the motor. reves with engine I think :S

No, this is only when I was towing hard up the mountain at 65-75mph and hitting up around 3k RPMs. Once the RPMs died down a bit you could hear something else kick up. It made me nervous. I was thinking it sounded like a bearing or something. I was hoping it was just an auxiliary fan. :D

I hear a similair sound, it sounds like near the firewall to me, I think I am hearing my CAI , cause I didnt hear it before, it only happens at like 1800 rpm and sort of lugging.

I hear a similair sound, it sounds like near the firewall to me, I think I am hearing my CAI , cause I didnt hear it before, it only happens at like 1800 rpm and sort of lugging.

X2 only mine is at 2200rpm...sort of rumbles ...disappears above and below the range... loaded or unloaded

the noise also happens with the a/c on.