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Discussion Starter · #1 ·
a lot of times if im driving my truck for the first time that day my engine will make a loud roaring noise and it sort of feels sluggish. after a little bit the noise will go away and the normal sound of the engine is all i hear and the truck behaves normally. my friends 05 duramax does the same thing.what the crap is this?? it makes me nervous like im hurtin the engine.
 

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When you first start out, especially on a cool morning, or if the truck has been sitting for extended period, the transmission stays in a "warm up" mode. It stays down in the lower gears longer which in turn makes the engine rev a little higher! Just from experience, the roar you hear is a combination of a cold transmission and high engine rpm!
 

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Roar

Thatz what I tried to say!
Thanks GM Tech for filling in the blanks!

Cheerz
 

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a lot of times if im driving my truck for the first time that day my engine will make a loud roaring noise and it sort of feels sluggish. after a little bit the noise will go away and the normal sound of the engine is all i hear and the truck behaves normally. my friends 05 duramax does the same thing.what the crap is this?? it makes me nervous like im hurtin the engine.
Morning Sickness

an unfortunate part of the fan clutch design. When you pull the truck in warm, some of the viscous fluid will migrate, locking the clutch for a few moments after the cold start. Most Thermo-viscous clutch designs have this annoyance.

We all suffer from it unfortunately, Male or Female. :)
 

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the worst vehicles for fan roar that ive heard are the trailblazers envoys raniers they have a very expensive electronic viscous clutch that turns on both by heat and electronicly. these things sound like planes taking off when they go out which is very often. a little off topic but makes you feel better that there are worse fan setups than the dmax
 

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Discussion Starter · #9 ·
so is there anything i can do about this its sort of annoying and sounds bad
 

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There is a solution to the "roar". You could remove your clutch fan and install a dual electric kit. There are a few manufacturers out there that sell these aftermarket cooling fans. Flex-a-lite Automotive Cooling Division has a dual electric unit for the duramax ( part#284 ) and claims a gain of 27hp, 34 lb-ft torque and 6% better fuel mileage. I'm not sure how loud they would be, but, you can research that. My truck roars constantly while I pull my 15,000# tri-axle trailer in warm weather. I won't switch to electric because they are not recommended when the combined gross vehicle weight (CGVW) exceeds 18,000 lbs.
Hope this helps.
 

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Discussion Starter · #12 ·
whats the difference between the stock fan and this aftermarket one and how much is it?
 

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The engine powers the stock fan via the surpentine belt. When the engine heats up above normal, the thermo switch tells the clutch to engage and the fan spins (roar). The electric fans run off the battery which is maintained by the alternator. The same thermo switch will turn on the electric fans when needed. I believe the system costs between $500-600
 

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There are couple of people here said to stay away from the electro fans, due to overheating. I had the same concern When I first got my lbz. Had it for 7 months, noise doen't bother me. Plus running straight pipe helps drown out the roar from the fan clutch grease.
 

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JackH will have to research that. Maybe start a new thread asking if anyone has tried the conversion.
 

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whats the difference between the stock fan and this aftermarket one and how much is it?
Lets nip this one right now.

the 27 HP claim is an outright lie. The reality is, it probably saves you 27 HP compared to the stock fan running at full tilt. The only problem with that, is that you can NOT tow anything that would otherwise survive the load that requires that fan. Remember, that is 27 HP consumed ONLY while the clutch is engaged.

These are not straight across replacements. The moment you put electrics on the truck, you lose 6000-8000 lbs of tow capacity from the cooling system. The manufacturers are not shy about telling you this, but they are completely dishonest about the power benefit.

Also deceptive, is the "5000 cfm" ratings they attach to them. Pure BS. What they forgot to mention is that rating is with fans not mounted to anything. All electrics are rated at zero pressure drop, in free air, which is stupid, unless you are going to hang them from the mirror to cool your face. Once mounted on the radiator stack, the enormous amount of resistance they encounter, reduces output to less than 1/3rd of this value. So again, pure BS.

Nothing is free. The 40 amps they consume is NOT free. The alternator gets very hot as it nears the limit of its rated output. It is going to have a shorter life. But while it is huffing down 40 amps, that is a 5-10 HP parasitic loss of power. Nothing is free, that is except the advice you are getting here.

AVOID! Complete waste of money.
 

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That all makes sense Charly. If JackH is not going to tow anything and lives in Alaska, he might be ok with electrics. My clutch fan only engages when I tow or if the outdoor temp goes above 90F. I personaly like the "roar" and the turbo whine.
 

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Discussion Starter · #18 ·
so yours only engages when its hot? thats wierd cause it seems like mine only does when the engine is cool like early in the morning when the truck has been sitting in the drive all night. after i drive it just a little the noise goes away. but if the truck has been sitting in a parking like all day int he sun it doesn't do it when i get in and drive.
 
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