:blahblah: I have an 05 GMC 3500 that tows every day. After reading countless posts on O/H issues I sealed the stack with one of Killerbees kits and have been very happy.

The Quandry: With last suumer a distant memory I forgot how loud the fan can be. We recently completed a 1200 mile trip towing a 14K 5er in temps ranging from 85-95. No problems with overheating as the fan did its job maintaining the engine around 210 and tranny under 200 the entire trip. My primary concern (gripe), however, is the engagement of the fan from a dead stop after coming off a highway or moving through traffic light to light. I believe I understand the cause of this as since no air is moving acoss the stack the fan closes and engages. My problem, however, is that when the fan engages from a dead stop it steals power when I need it most. In addition, it is extremely loud at this point and is incredibly annoying. I have of course been informed by my dealer that this is normal, yet I have talked with several duramax owners (Mostly 04 owners) who do not experience fan activation as I have described above.

Question 1: Is it normal to experience fan activation from a stop when towing @ ambient above 80 degrees.

Question 2: If this is in fact normal operation for an 05, would an electric fan such as the ones offered by flex-a-lite (www.flex-a-lite.com (http://www.flex-a-lite.com)) help remedy the annoiance of the clutch fan while still maintaining proper temperatures.

I appreciate any feedback you could provide.

When we are towing and in stop and go, ( or accelerating from the side of the highway) the lack of air flow cripples our trucks in more than one way.

As you have stated, the parasitic nature of the engaged fan robs HP when it is needed.

Additionally, with stagnate air flow, the IAT ( intake air temperature ) soar.

High IAT reduces the efficiency of the turbo, this situation is multifaceted and well documented.

FWIW.

Mine has done exactly what you described when towing and stop and go movements.

I know an electric fan can't replace our stock fan (this has been beaten to death), but could we use an electric fan to increase airflow for the stop-n-go stuff like this (turn on in stop-n-go; turn off when cruising)? Would this derease the amount that the stock fan is being used at all? Or would the electric fan's blades slow down the airflow already coming into the stack when the truck is at speed?

Joseph

I don't think there's anyway to fit electric fans between the stack and the clutch fan, if you're referring to putting "pushers" on the front of the stack, they're very inefficient and will block airflow after 30-40mph. At least this is what I was told when I asked a couple of my mechanical engineering buddies.

Very normal.Do some simple mods for towing to give you back power plus more to conquer hills.Your truck will thank you.Mine did.

I would try lowering the back of the splash shield.. Members have reported this helps the hot air excape the compartment and might help a little when your standing still waiting on a light...

Mine does the same thing when I am pulling....

A real eyeopener for me was the amount of HOT air the truck sucks in when standing still... I put on and tested one of Tx's CAI and that solved that problem... Well for about 3 minutes... Once your sitting still all the temps are going to start rising... Once moving the CAI brought the intake air to within 2 or 3 degrees of ambiant temps.


Good luck

Your stealing my story ToddSr. :) I have the same thing and this topic has been beaten to death on this forum. I think a couple of major solutions are in the future. We'll have to wait and see at this point.

BTW, my 02's fan never came on when hauling my 37' 5er. When the 05's fan ran for the first time, I thought I slipped the tranny!