I have been doing some investigating because we all seem to experience this problem. There is a TSB for this and I might be partialy right when I thought it might be caused by having your AC on before you shut the truck down. Seems the the viscous fluid that activates our clutch fan does not return to its starage area (within the clutch). TSB says it " Migrates", and after you start the truck, it slowly begins to return to the starage area untill its needed to put the clutch in full pitch. Thought you guys might want to know, I did.


mike

I forgot to mention that this is normal and you should not worry about it.


mike

Glad you did the research, I notice they all run when cold, never took the time to find out why, just wrote it off as a charecteristic..

Mine runs sometimes when cold..always thought it was weird..but i never run my AC..hmm

Nick


I am not saying AC has anything to do with it, it was only a guess on my part. I found this TSB in the trans section of Mitchell On Demand. Seems there were trans slip complaints when in all actuallity it was the fan clutch.


mike

Nick


I am not saying AC has anything to do with it, it was only a guess on my part. I found this TSB in the trans section of Mitchell On Demand. Seems there were trans slip complaints when in all actuallity it was the fan clutch.


mike

It actually is effected somewhat by underhood temps at shutdown time. With A/C temps can be higher but with a hot engine at shut down, a lot of heat bleeds out past clutchfan heating it up before engine cools down sometimes.

Good insight snoman! Almost all fan clutches work this way, with the same shortfall. The fans on these HD's move more air and make more noise than about anything out there. When you lose 15-25 HP and gain 30 dB in the cab, you think something is wrong. I think it is not the best design. It could be fixed if GM cared. My thought is to take the transmission cooler, which doesn't do a good job anyway, out of the front end, it is hindering airflow better than it cools the trans.


Present design is completely autonomous (dumb) yet effective. GM has produced an electro-viscous clutch that will take logic input to activate it, i.e. water temp switching, AC on, etc. Don't know if it can go in d-max.


Edit: looks like GM is going to use the electro-viscous clutch in the 05's, will increase fuel economy and eliminate pooping of the pants at high speeds.Edited by: masterp2