Changing the fan duty cycle settings in the ECM does help at highway speeds. It actually helps at all speeds. They aren’t dependent upon speed but actually on the temperature of the coolant. It sounds to me like you have a diesel swap in your truck which is a completely different ball game to what we are talking about. I agree that upgrading the tranny cooler is a must but it still shouldn’t be the only thing that is done. Like I stated earlier in this thread the factory programming for the fan duty cycles is crap and doesn’t move a lot of air until it starts getting harder to cool the engine and trans down. So again yes it will help at highway speeds. This isn’t a clutch fan setup, it is electric cooling fans.
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I really really really don't like to argue with anyone on the internet.. I'm too old...
But I want people to know the facts>>>>>
Your electric engine cooling fans will NOT be commanded to turn on NO MATTER what
the coolant temp is at highway speeds...
Maybe you have a custom tune that does command them to ON at 60mph,
but it really wouldn't have any benefit due to the incoming air at speed anyway.
This is the reason the OEMS do not do it.
IF yours turn on at 60mph, then you have the unicorn... I do understand the differences in mechanical, electrical, viscous types of fans that the oems have used
for over 100 years
I do not have any "swap" crap in my rig. It's the factory engine, trans, diffs, etc/
I do have a supercharger and a tune of course.
My fans are programmed to come on low speed at 202* and high speed at 212* ..
I can watch my duty % at all times so I know exactly when the fans operate.
But as stated, oem electric fans don't come on at 60mph..Now, if you slow down then
they do come on and will run on high if temp demands it. But keeping cool at a steady
60-70 mph while towing on grades in 90*+ weather presents a whole different set
of parameters