I have heard all the stories about the fan clutch, I have heard it also. But yesterday I took my bobcat to the dealer for service and the truck pulled it like crap. It sounded like the noise that I thought was the fan clutch, then I thought that it was the temperature outside, it was about 90. The transmission gauge was 200. Today when I picked it up the outside temperature was 81 and it did not do this and it pulled great until I got back to the jobsite where I had to put the truck in 4wd to pull the bobcat up a very steep gravel grade, then it started making the noise again and it almost bogged down and did not want to go up the hill. I had taken the bobcat up this hill two days before and put it in 4wd and it was fine.

What is the problem. HELP please .

Thanks, Doodle

I had the same “noise” and power issues when hauling my heavy camper up steep and I do mean steep grades in the sierra mountains last week. Some people say fan clutch, but I don’t think that’s what it is. It was happening so often that finally one of the times it happened I floored it and it seemed like it went to another gear and the sound went away. If it was the fan clutch noise as averyone says it is it would not have gone away just by flooring it. I think the sound comes from the tranny shifting and staying in a lower gear. http://www.cssevents.com/Bigfoot.jpg

Mine does it too. At high air temps or high altitude, it goes WHIRRR!!! and loses significant power. The tach needle doesn't move, so it's not shifting or slipping.

I just purchased my duramax a few months ago and having the same problem. I think it would have to be the fan clutch took it to the dealer they said nothing is wrong, I do not really believe them. Any info on this would be great

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Fitter 48093 what was your truck doing when you took it to the dealer? Did it have to do with this fan clutch noise? Thanks

I really hate to be a "me too" but, me too!


It does sound like a blower or fan of some type but could be the transmission. I'm leaving tomorrow for a trip to Cody, WY. There should be sufficient challenge there to study the problem in more detail. So far, the problem only seems to occur when towing and under a load (long, up-hill). Interestingly, when it occurred, I checked the temp gauge and it was steady. In other words, no obvious change in operating temperature, both transmission and coolant.Edited by: Dick

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<TD id=HB_Focus_Element vAlign=top width="100%" background="" height=250 UNABLE="off">Mike, Well it did have some noise too it. (Read my post for yesterday"Need Help Quick") I do have more information about the test performed. After a number of differant diagnostic test they did a leak down test both in park and in drive and found the #2 injector to be 4.4 in park and 4.9 in drive, with the others being 1.9 and 1.5. So they're going to change it Monday when the part becomes available</TD></TR>
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After it happened enough for me I started playing with the speed and tranny and the tow haul mode and the Overdrive dissable button, and at time with all this playing and pushing buttons i can duplicate the sound and - it is NOT in my opinion the fan clutch.

If it was the fan clutch it would stay on till the engine cools down or conditions change, and I could not make it go away at will.

With what I was doing I could duplicate the WHIRRRRR sound and then make it stop by depressing the throttle.

Now I have done some reading since I got home ( this all happened last week) and coincidently the tranny has few tricks in it, one is the GRADE BRAKING system, the other is CRUISE STABILIZATION, and tthey are calculating your
Throttle position
Brake state
Vehicle acceleration/deceleration
Grade/Load
Vehicle speed

And I found out Grade Braking can be exited by depressing the throttle.


So that gave me a Hmmmmmmmm.

My thoughts are it’s the tranny not going to the next gear either because of the steep incline I was on and all the fluid was pushed to the back of the tranny, or it was just hanging there in Grade braking ( even though I was going UP ) until I slammed on the throttle.

After I finished jamming as many buttons as I could think o fto break the thing it then would be ultra smooth and not go into it’s WIRRRR mode for a while, then after a while it would pop up again and again I would make it go away by slamming on the trottle, till the speed of the vehicle took me out of the WIRRRR.

Who knows???

http://www.allisontransmission.com/service/faq/index.jsp?CategoryID=11

Here is the link to the FAQ about Allison stuff - Note the info on gradr braking and Overdrive dissablehttp://cssevents.com/Bigfoot.jpgEdited by: Kendall69

Sounds like the inner cooler temp was bringing the fan on. Mine has come on a few times on long, steep grades towing. In each case the water temp was at 200 and the trans between 180 &amp; 195. Later! Frank

My LLY has the same issue. I dont think its a tranny issue, I definatley think its the fan. Ive griped before about the fan kicking on on some mornings right after start up and staying on for 1/4-1/2 mile and then going away.


This past weekend towing 8500 of trailer, the thing kicked on on just any hill with moderate throttle application. Roll onto the hill, roll into the throttle...WHRRRRRRRR...crest the hill back off and it goes away. My Cummins used to do this occasionally when running her real hard, and the sound is unmistakenably the fan to me...


Ive also tinkered with settings, TH, OD lock-out, more throttle, less throttle....didnt matter. In warmer weather towing 8500# with the AC on, the temps would climb one small line below 210. Driving around empty, Im about 2 small lines below 210 and the fan/noise hasnt presented itself. When the fan/noise kicks in, the temp gauge doesnt move...one would suspect that it would.


Power does fall off and it kinda irritates me that it does. But thats why they run fan clutches- so you arent spinning that big arsed propellor all the time. Power and fuel eco are improved with the clutch.


Im going to try a couple things to keep her cooler and see if I can prevent her from getting warm enough the clutch has to kick on...

I hate to say it but i've had my duramax for 3 weeks and the same thing happens. You hear what I think is the fan revving up hard then my truck sorta jumps like it engages hard or somthing. Only time I feel this is when towing my bobcat or the heavy dump trailer.

Backcountry -The one time when I kept at it to either duplicate or eliminate the WIRRRRR, was when the WIRRRR came on I was climbing with a heavy camper load steep grade, it started to WIRRRR and a tramed on the trottle and sped up again going up hill and it seemed liked it caught another gear and went away.

I did it every time after that and the WIRRR went away and all was fine.

Prior to NOT slamming the trottle down the WIRRRR would stay on indefinately and never bring the temps down and never improve the situation. For me anyway the cure was the throttle.

I would love others to try the trottle trick and see if it works on their rigs.



http://CSSeventS.com/Bigfoot.jpgEdited by: Kendall69

Like a dog with a bone, I called Allison and described the WIRRR, and he said it could be a "partially clogged paper filter in the pan"

When I explained some guys are having the WIRRR occur in the morning during start up as others here on the site have stated, he said, yep that will happen when the fluid is "thick"

I don't know guys, it doesn't make sense to me, but he did say tell the dealer that I talked to Allison and they said to change the "paper" filter in the pan. He also knew that it would not throw any codes as others have found out.

Anyway for what it's worth.

WIRR is going to be proportional to engine speed. So, if you upshift it might seem to get quiter. I am having a problem with sufficient cooling. I think that there is a broad problem here. Dealer told me that combustion temps are higher on the LLY. Wouldn't that mean higher compression? Did GM compensate enough with the cooling capacity to overcome this? Is the water pump and radiator the same on the 03's? What about the fuel mileage, is this all linked? If the fan is engaging more, then fuel economy goes down.

i don't think fuel mileage is a problem, i still get 19 empty and 17 pulling the bobcat, also mine did make the noise on flat groung and when pulling. i did depress the peddle and let of of it and their was no change. i think that we may have a problem.......????????

19 and 17 with an LLY? WOW!

Kendall69 I wont be towing for a couple more weeks here, but Im certainly interested if something is going on here.


The wrrrrr I describe is decently loud....in the AMs with the window sounds like an old Army jeep from a old episode of MASH driving around....

mine has never done this in the am. both times it was around 4:00-6:00 pm.

doodledumb, when you floored the throttle did you get up enough speed to go to the next gear, or until the WIRRRR stopped?. That was the key for me, I floored it till the WIRRR went away, and it went away when it seemed to hit another gear.

Believe me I know all this sounds weird, but enough of us are having the same problem and the stealers are telling all of us we don't have a problem, and " it's not throwing any codes"

Looks like one of us is going to have to load up our trucks with a heavy trailer and put the service guy in the truck and hit a close mountain road, and say EXPLAIN THIS.

I have 04 LLY/ally CC/SB. I hear the fan sometimes in the morning. Haven't pulled much with it, small load of moving stuff and small utility trailer. No loss of power. I get 18-18.5 mpg. Had a high of 19.2 and a low of 16.4 mpg. From what I'm seeing/hearing this is about normal for mpg. I haven't heard any other guys I know with LLY complaining about this fan noise or loss of power, but it does peak my curiousity.

I'm gonna shoot a hole in the Allison theory ... I have the ZF with the same symptoms.

Many times (but not always) I hear the fan for the first mile or so of my morning commute, while the motor is still cold. In fact, I've heard it on very cold mornings. No rhyme or reason to it. Except I'm POSITIVE it's not my Allison, 'cuz I ain't got one.

I'll also get the fan noise when I'm working it hard, pulling trailers up hills on warm days, etc.

I really think it's the fan.

My dealer has offered to test drive with me and the trailer. I just don't have time to do that. Might be interesting to mount a remote temperature transmitter in the engine compartment to see if temp and wirr correspond.

ZFMax, my theory isn't "just Allison" as much as I think it's TRANNY related rather than fan clutch related, so actually you are confirming the tranny theory.


Two points, (1) why would the fan clutch go on in the mornings when the engine is cold. The fan clutch is designed to cool the engine - and the engine is already cool.

(2) if it's not the tranny why does it go away ( at least for me) when I speed up, if it was fan clutch it would stay on longer since I am compounding the high temp and straining the engine even further by "gassing" it up a mountain steep incline.
I don't have the answers, I'm only running through scenarios and trying to tame the WIRRRRRRRR.

Now I'm not saying anything is wrong with the truck, tranny, or cooling system. I just want a answer to what is causing it and why - so I can adjust my driving to avoid it, or work around it.

I don't have any big hills near my dealer or you can bet they'd be in the truck. I don't think they'll let me have a service writer for a 1/2 day.

The only real way of proving it would be to monitor the fan operation.


Since there is not enough room in the engine compartment for a circus midget to sit...


Either a camera or a bicycle tach. A bicycle tack can be had for $20. You would mount the magnet on the ROOT of the fan blade (too much force on the outside) and mount the pickup on the block.


You might find the data using a Tech II or similiar scanner as well, but I've never seen that perimeter.

I had the same problem last week. The "whirr" started when I was pulling my 5er to the campground. About 10 miles down the road after many stops and starts on a 90 deg. day, it started. It would go away just as Kendall69 says when you accellerated and got out of 3rd gear. It would come back after stopping and re-starting but only intermittantly. When I un-hooked from the 5er, we had to run an errand and the noise was still there as we exited the campground. Once I made it past 3rd gear, the noise went away never to return.


After that, I thought it must be due to the hot day and all the sarts and stops with the trailer. I am in Ohio, so we are not talking big hills. On the way back home from the campground, I tried to make the noise come back. I ran it hard and had the tranny temp up to 200. I even passed a motorcycle on a two lane road with the 5er in tow, so no loss of power involved. The noise did not return.


I am interested if anyone has tried the internal paper filter change. If this works, I may go to the dealer and demand they try it. I will use this page as a reference to demonstrate that the problem does occur even though we can't prove it. Lets face it, as much as these trucks cost, any D-max owner has to have better things to do than drag a heavy trailer and a tech around hoping the stupid noise kicks in. Keep me informed on all your efforts and I will do the same.

The 6-speed has no slip device in it. Nothing to whirr. No automatic engagement or diengagement of anything going on, and the disappearance of the sound has never been tied to a gearshift (although running the motor up in rpm when it was doing it cold seems to help kick it out).

I guarantee you the noise I'm hearing is the fan. My previous truck (brand F) did this too, although never cold. I know what a fan kicking in sounds like.

I have no explanation why it sometimes kicks in on a cold motor. I always figured the clutch fan was afu, but never wanted to hassle with trying to convice the dealer of it, figured there was a slim chance I could reproduce it for him and it didn't seem to be hurting anything anyway. I figured I'd wait until it just got stuck on and then take it in. But it's never gotten worse. Interesting to hear that others have the same symptom. Must be something inherent in the fan clutch design. Guess I won't worry about it anymore.

Kendall69 do you think when you speed up that might let the truck get more air so the clutch can kick out?

I thought the loud whirring noise was to help the engine get up to temperature quicker. I though I read somewhere that the turbo restricts the exhaust to increase load on the motor....or something like that.


I have only heard the noise in the morning and it goes away as soon as temps reach 165.

bobbss I don't think I got up enough speed for more air, because it clears in a short distance, but anything is possible and that is a great thought.

Next time out I am going to keep better notes on speed, temps etc. to nail it down.

Allison seemed to know of the WIRRR and knew exactly what I was talking about. I didn't have to explain conditions. temps etc. he went right to the paper filter solution - followed up with " if I didn't want to try that , then I would have to live with it".

I'm convinced enough of us are onto this anomaly, that eventually we will get definitive answers soon.

I have experienced the wirr with my truck. It occurs on my truck while towing. My wirr occurs when I stop at an intersection after a tow down the highway. When I accelarate from the stop a loud wirr begins for 1/4-1 mile in length with a perception of a loss in power. I thought it was the fan kicking in. Also, my temps are in the normal range. Maybe they have the fan set a little to sensitive.

It is the fan cluch and it occurs in the morning becuase the fluid in the clutch is not to opperating temperature (more viscous). This is normal in the morning but should not be happening at 75mph with no load.

Today coming home in 90+ heat at 75 the wrrrrrrr sound came back. Looked down and engine temps where normal and so where tranny temps. Took about 2 miles for it to finally go away. Wierd

Im going to try to block off air flow to my radiator and test in the driveway to duplicate the sound. This is per the test procedure for the fan clutch. Cover the rad, set RPM to 2K, and wait for fan to kick in. Fan kicks in, uncover, run to 2500 RPM, wait for clutch to disengage...If the wirr sounds the same as the clutch, then as I posted earlier, I'll look at ways to keep her cooler. If the sound isnt the same, then off to the dealer I go to get the paper filter changed...


One thing I thought about- when does the EGR cycle? What event/throttle pos./load etc make the EGR cycle. The EGR is going to raise the air inlet temps...

I have the same problem with my dmax it is definitely the fan clutch. I can drive down the highway at 70mph and the whrrrr comes from the front of the engine, besides my tranny never downshifts and the temperature does not go up. Interesting thought on another post I created about the same problem though. The fan clutch reacts to the trans cooler, a/c condenser, turbo charger intercooler, and radiator so maybe the intercooler or a/c condenser are the problem since we have guages on the rad and tranny. Either way there is a problem so much for my dmax being quiet...

Just chatted with my local service manager and he told me the system is working just the way it should. He wasn't all that sure about all the sensors involved, but it definitely is the fan kicking in to draw more air over the radiator. It also seems the sensors act in unison to anticipate additional cooling demand before the temperature changes are obvious on the dash instrumentation. As far as the noise is concerned, I take satisfaction in knowing the system is working as it should. If I stop hearing the whirr under heavy load, I'll be headed for the nearest service center.





As an aside, I just returned from Yellowstone and the LLY worked perfectly. This included some lengthy pulls in 95+ temperatures. Yes, the fan came on when it was needed and only twice did the water temp rise above 210. Maximum transmission temp was 185.Edited by: Dick

Sure sounds like the fan to me, they should come on and off alot in warm weather. The temp guage should not move much. The AC, Trans, and intercooler all affect this and it is normal to be engaged at first when its cold just for a short time. I dont really know why but they all do it. I dont know what the lly has for a fan clutch but if it is still a viscous coupling they work totally off of the temp of the air flowing over it. the covering the radiator trick is how to test it and it should roar like crazy when completely locked up. TROY

Had this problem too. Have good diesel tech (Mack @ John Elway GMC in Denver) that ran it back to the paper filter on the Allison. It needs to be changed before the truck hits 7500 miles as part of the break in procedure - not doing so causes high tranny temp and op temp, and excessive clutch fan noise.


- Rob


2004.5 LLY 2500HD CC SB 4x4 Duramax
TransferFlow 70gal
Monaco Coach Lakota 31SKT 12,500# Triple-Slide Fiver


21,000+ GVWR and pulling the continental divide most weekends.


http://www.dieselplace.com/forum/uploads/89E_rig_sm.jpg

Ok, boys and girls. I changed my paper filter two days ago ( I should say that my dealership performed the work based on their trust of my word that Allison says to change the paper filter under warranty if you have this reoccuring noise problem - I doubt there are many dealers out there like that!). I am about to go on vacation pulling the 5er through mountains. I will report back on or about August 2.

My 1996 1500 5.0 did this. My 2003 2500 does this. And now my 2004 3500 does this. I always assumed it is the fan, well for at least the last 8 years.

Master44Mag,


Good luck. Hope changing the paper filter helps. Next time mine goes in for a drink, I'm going to do it as well.


Thanks,
Dennis

Master44Mag, please let us know if this helps. I have pulled my bobcat several times in this Georgia heat, and it will only do this when it wants, but the last time I had to pull down the expressway and it was bad. But when I got off at the ramp it was very loud and when it changed into lower gears it got worse every time it sounded like a manual. I tried with the tow/haul on and off with the air on and off but their was not a change. I almost went to see the dealer with the trailer hooked up like some have suggested. I guess if the filter does not work I will do this. Thanks Doodle

It is the fan.


I had a 95 S10 Blazer that the dealer bought back after four months because the loss of power was so bad, the thing was undrivable. The reason you cannot relate it to engine temp is that the a/c is the culprit. Govt regs and loss of Freon are at the root of this problem. They can't get enough cooling out of the R-134a without air movement. I got a 96 Tahoe after the Blazer it did it to, but had enough muscle that...I put up with it. With the 02 DMax, it's come on occasionally, but not anything like what is described in this thread.


My guess is they reengineered something about the fan, perhaps increase the pitch of the blades because of complaints about not enough cooling etc, etc, and they get the reverse effect of complaints about the fan and loss of power. .

Hello all I am a total newby here. I do not own a pickup with a durmax yet, but will soon. :) Any ways has anyone tried removing the fan all together and installing a high quality electric fan in is place? Just a though. Also have any of you who live in very hot climates tried swaping out your radiator for a better one? Another though (keep in mind I am not very knowldgable about the functionality of a Tech II) has anyone hooked one up to read the real time temp of the motor/trans, ect... to see when and where the fan is set to engage and corrlate that with the noise?