Loud Fan Noise

[strokingmyego]

I was pulling a steep grade the other day (7-10%) with my toy hauler that weighs about 8500lbs. wet. The road was wet and it was raining so the road was a little muddy. I had to engage 4wheel drive to help keep rear tires from spinning as much. The cooling fan kicked on as it should and all was well for a while. Then I noticed that the trans temp was starting to go up a little. Thats when what sounded like another fan kicked on that was very loud. What was weird to me is that the fan sound was RPM specific in that the more RPM's the louder the fan got. The Trans Temp dropped to normal operating temps YAY! This fan or whatever continued to run until I got to the camp site and let the truck cool down. A few weeks later it came on again while pulling a 4wheeler trailer up a 13% grade at about 4000lbs. Just want to make sure all is normal with the excessive noise coming from this fan.

Thanks!

[LHMissions]

There is but one fan on our trucks - and it does tend to cycle from loud to louder as your pulling up a strong grade.

I tow generally pretty heavy through the Appalachian mountans on a regular basis. My fan kicks on at about 240* coolant temp and as I am climbing the long grades - it will cycle on and off (lound to louder) till I reach the top and then continue to run until temp drops off about 40*. Then its back to normal.

I have heard the veins in the turbo also cycle under load but not sure this has anything to do with the sound your hearing.

[superxcrewfx4]

He is correct it is variable speed and from what I have personally heard in 6.0's it has about 3 speeds, small plane to stealth fighter!

[ThirdCoastStroker]

i hear my fan like that very often even when i am not towing but then again the average heat index around here all summer long is like 115* so i just figure that is normal for the fan i guess i will find out come winter time when the temps drops down to around 80* or so because thats about as cold as it gets down here

[strokingmyego]

I am pretty sure that it was a fan that I was hearing. In both cases I was only going about 10-25MPH with very little air to flow over the radiator and pushing the truck pretty hard. Just weird that when I let of the gas the RPM's on the fan would fall and then reapply gas and RPM's and sound increase. I always thought fan stayed on constant until Temps fall. Max RPM's on fan equal very loud!!! Hard to talk over it!

[ThirdCoastStroker]

yeah mines the same way when i take off from a red light my fan will run till i hit about 20 mph then stop but like i said it is f'in hot down here

[superxcrewfx4]

6.0's have a strange little sensor that decides as to what speed it goes and how it works

[RobertS450]

Originally Posted by strokingmyego

I am pretty sure that it was a fan that I was hearing. In both cases I was only going about 10-25MPH with very little air to flow over the radiator and pushing the truck pretty hard. Just weird that when I let of the gas the RPM's on the fan would fall and then reapply gas and RPM's and sound increase. I always thought fan stayed on constant until Temps fall. Max RPM's on fan equal very loud!!! Hard to talk over it!

The reason the fan sound changes with engine speed is because the fan speed is changing as its belt driven off the engines crankshaft. As for going that slow with that much weight up that kind of grade you should probably use 4 low so that the torque converter can get into lockup and help keep the trans temps a bit lower. I'm new to these ford trans so not sure when the TC can go into lockup, the dodges have to be in 3rd gear before lockup can accrue