Which upgraded fan is better?

[turbovanman]

I know, its probably somewhere but in a rush, I see the Dmax upgrade and Kennedy sells an 20" metal fan upgrade, then shows why the Dmax fan is a bad upgrade? Kennedy also sells a recalled new clutch.
Anyone agree or disagree, need to get one ordered asap for a customer. Thanks.

Oh, he has a 96 automatic Dually with a new engine, 4 inch exhaust, turbo master set to 12 psi and a recalled computer. He tows an average sized trailer, I would guessa round 30 feet and goes up some serious hills.

 

[OregonHorseTug]

I've got the Kennedy super fan clutch and went with the 9 blade steel fan. I haven't had a cooling problem since. But, when it kicks in it sounds like I'm going to vacuum up the road. Not a bad thing just doing what it is supposed to do but some folks don't like it that noisy. You can see the load I pull in my sig. I regularly pull up 6% grades on long pulls.

 

[Acesneights1]

It really depends on which WP you have. The Heath one only fits the 99+ WP Spin on. The Kennedy one fits the 4 bolt WP only. I personally think the 9 blade steel works best but you can buy a Hayden SD clutch(the one Heath and Kenndey use) For about 150$ and then do the mod to it. The Spin on WP is supposed to have a better balance flow.

 

[robzombie4551]

Dmax fan is better IMHO because of the light weight, less stress on the WP bearings and better balance. I run one with the stock clutch 1/8" mod and it comes on at 195. Even towing up 8% grade it didn't go over 210' for 7 miles.

It works for me and whatever you chose will be better than stock.

 

[WarWagon]

The Dmax fan will pull more air at idle. It has more pitch to work with lower RPM and high airflow. The downside as the site says is it slips the clutch more at full speed.

You may have to trim the shroud for clearance with a 21" fan.

20" steel is also a lawnmower blade with a ton of inertia. Smack an elk and the fan does serious damage before it will stop - the belt will not transfer that much power to the fan vs. it's own inertia. Ever see a steel idler pulley bent out of round with a fan blade wadded up under the compressor between the block?

Know this: the lower kick on temp clutch with a lower thermostat keeps sudden WOT hill load from spiking over 210 by the time the fan can kick in from the thermostat opening and radiator heat. It takes a bit to cool it down and kick the clutch out. The spring heat up and then fluid movement delay in the clutch is almost a fixed time - a unavoidable trade off design limit in the thermal spring viscus clutch vs. a on/off clutch.

I would suggest:
185 T-stat
HO 4 bolt water pump 1998 year is ok.
The low cal Kennedy clutch. (I love and miss the clutch that impact died with an elk.)
Cleaning the radiators including removing the oil cooler to clean.
Possible new/re-cored radiator depending on buildup in old one.

21" or 20" fan is then your call. Highway speed all the time go with the 20" for longer clutch life. In town and AZ 105 degree I NEED AC go with the Dmax fan. Here in AZ with a full load and 28' long 8' high full width race cargo trailer I could not go over 210 with the above setup on 20" steel. 14 PSI sustained boost and 1/3 turn on a DB2. Fighting altitude and Payson, AZ 10% grades...

Without a HO pump your fan upgrade alone is not enough. Dual stats are not required.

 

[turbovanman]

Great info guys. Forgot to mention, both have the HO pumps, I put them on.

Looks like I'll go with a Hayden SD fan, mod the spring and get Kennedy's steel 20" fan. Thanks.

 

[WarWagon]

For a customer ... Not sure I would warranty a spring mod. Rather get a calibrated clutch and know it will work as advertised with no customer comebacks. Friend, free labor, or beer is different.

 

[racer55]

Another note for the duramax fan is that besides trimming the shoroud you need to have good engine mounts,if the engine rocks at all the clearance you made in the shroud can dissapear.

 

[robzombie4551]

No trimming was needed on mine. And my mounts have 220,000 miles on them. I have 1/4" clearance between the fan and shroud.

And man does that thing pull the temps down fast when the clutch locks!! It pulls air like no ones buisness!!

It was by far, the best mod besides new rad that I made to stay cool while towing.

My clutch doesn't slip at all when locked, maybe if you have a worn out clutch it will slip but that would go for any fan setup.

Dmax over steel any day, lighter, better balanced, and if the fan has an issue I would rather have plastic fly around versus steel.

The steel fan might last longer as I have 30 year old steel on my 68 gs 400, but to each his own.

 

[tanman_2006]

I have plenty of clearance for my dmax fan, like an inch all around. I moded my clutch a hair. It keeps temps down great at highway driving and around town, it almost has trouble warming up when outsie temps are below 70-80. When it kicks in towing temps drop rapidly. Clutch could kick in a bit sooner as it gets a bit over 210, maybe 220 better than the nearly 250 i saw once!

 

[WarWagon]

My clutch doesn't slip at all when locked, maybe if you have a worn out clutch it will slip but that would go for any fan setup.

Slip is how the clutches operate at all times. This is why they have huge cooling fins on them, to remove the heat from slipping. Totally disengaged the fan is being driving at 10-20% of input shaft (water pump) speed. Full lockup only gets you 80-90% of input shaft speed. A larger load than the clutch is rated for will give you say 70% of input shaft speed with the 10% additional slip going to heat generation in the fan clutch.

Old worn out clutches loose 200 RPM per year simply by the fluid aging or leaking out. Thus they are unable to deliver full fan speed when needed. (Not reaching the 80-90% of input shaft speed although they will try and just not make it.)

The only reason we do not have horton on/off total lock up clutches is because vehicles do not need 100% lockup most of the time and you can get better linear temperature control with the viscus clutch. Going WOT up hills is a rare case vs. everyone else who usually doesn't need this kind of cooling. The people who don't need 100% lockup are the ones complaining about fan noise and lower MPG from the fan coming on early...

 

[turbovanman]

Interesting, I've modded customers before and no issues.

I emailed Kennedy and he said the fan's don't really do much, its the combo of his special clutch and fan that do the business, now I am really confused, sigh.

 

[buddy]

Just get a regular HD clutch and mod it to engage at 205 or so. I have DMax fan and agree it pulls a lot of air at idle if in hot climates thats good, and apparantly it helps keep PMDs on the intake alive, because mine has been there 3 years with that fan too. I would keep single stat if its there and keep 190 or 195 ACDelco. These engines run most efficient when warm, and do just fine at 200F.

 

[turbovanman]

Just get a regular HD clutch and mod it to engage at 205 or so. I have DMax fan and agree it pulls a lot of air at idle if in hot climates thats good, and apparantly it helps keep PMDs on the intake alive, because mine has been there 3 years with that fan too. I would keep single stat if its there and keep 190 or 195 ACDelco. These engines run most efficient when warm, and do just fine at 200F.

So your against putting a different fan on? Our climate is fairly mild but the main concern is his truck gets hot going up hills, so I need to control that. I know modding the fan clutch will help alot but would also like some more piece of mind. The Dmax is a good choice due to its weight but it flows alot around town, not really what we need, the metal fan works in the higher rpm range but weighs a ton and even Kennedy says its won't do much without a matching clutch!

 

[bobbiemartin]

Slip is how the clutches operate at all times. This is why they have huge cooling fins on them, to remove the heat from slipping. Totally disengaged the fan is being driving at 10-20% of input shaft (water pump) speed. Full lockup only gets you 80-90% of input shaft speed. A larger load than the clutch is rated for will give you say 70% of input shaft speed with the 10% additional slip going to heat generation in the fan clutch.

That is why I went with a Hayden "Truck Fan Drive". It has the same specs as far as temp on and off, turns at 80-90% when engaged and 20-30% when disengaged. However, it has 150 square inches of land and groove working area vs. only 72 square inches on the Severe Duty. According to Hayden, it provides cooler running and longer life expectancy. The one I use was designed for a Duramax in a medium duty (Kodiak, Top Kick) truck. It fits the threaded 6.5 water pumps.

 

[robzombie4551]

I emailed Kennedy and he said the fan's don't really do much,

Of course he's right, He's trying to sell you something. If the fan doesn't matter why would he try to sell the combo.

Just get a regular HD clutch and mod it to engage at 205 or so.

Buddys right, and others have said the same thing, that's why I dmaxed and modded my clutch and have been trouble free since. I even had to back off a little on the clutch mod because the dmax fan was way more effecient than the stock steel one.
From what I understand the kennedy clutch comes on to soon and stays on to long.

 

[turbovanman]

Ok, I'll stick with a Dmax fan then and a modded new fan clutch. Thanks.

Edit, just ordered the fan from my local dealer, $90, now to order the clutch from Rockauto, around here, its $250, ouch!

 

[tanman_2006]

I like mine set up like that. The next mod I want to do is a 98 HO water pump. I think the dmax fan is light enough that is still easier to spin even with the high pitch at idle, when the clutch kicks in nothing is easy.

 

[robzombie4551]

For what it's worth my fan only comes on at 195/200 minimal lock, 205 and full lock and holds or drops temp depending on the grade and my egts.

If I stay at 11/1200 sustained it will hold up to 210 until I let my foot out of it and then temps drop like a rock back under 200* and when they get to 195 the clutch unlocks because I don't hear it anymore at that temp.

 

[Acesneights1]

That is why I went with a Hayden "Truck Fan Drive". It has the same specs as far as temp on and off, turns at 80-90% when engaged and 20-30% when disengaged. However, it has 150 square inches of land and groove working area vs. only 72 square inches on the Severe Duty. According to Hayden, it provides cooler running and longer life expectancy. The one I use was designed for a Duramax in a medium duty (Kodiak, Top Kick) truck. It fits the threaded 6.5 water pumps.

I have the catalog. Have to look that one up.
WW,
The SD clutch according to Hayden( I actually spoke to them) Provides 90% lockup. The stock Clutch at best about 75%
I personally believe a Horton Setup would solve the overheating issues but they no loner make one for a 6.5TD but I have not had time to look thrrough the catalog but Bobbie just gave me an idea....:devil: