I've got 1500 miles on my 05 Duramax and so far I'm real happy but I've got a question about a noise we heard last weekend while pulling my boat. The boat and trailer weighs around 7000 lbs. which was no problem, but most of the time when I accelerated from a stop there was a rather loud roaring noise in 1st and 2nd gear. Almost sounded like the engine was reving way up but it wasn't. The roaring slowly faded out as RPM's increased in 2nd gear and stopped when it shifted to 3rd. I know noises are hard to diagnose from a verbal description but hopefully someone can help me before I call the dealer. Maybe this is normal but if it does this pulling 7000 lbs. what's it going to sound like when I pull my 12000 lb fiver? Thanks for your help.

Is it the cooling fan?

sounds like the clutch fan kicking in and out

I am willing to bet you heard the sound of the fan coming in then going out after it did its job, which was made easier as speed increased. The sound is a loud roaring sound and is very much like the engine has downshifted a gear and gained some extra noise. Was it a hot day out?

If I were you I would be glad to be hearing that sound, it means you are doing fine and are way ahead of the game.

.

how do i post anew topic ?

When you are in the "threads in forum" section (the one that shows all the various threads, like all of these in the 2004.5+ duramax section) look for a button at the top left that says "new thread"

Click on it and have at it.

Its your fan clutch.

You stated....
"Maybe this is normal but if it does this pulling 7000 lbs. what's it going to sound like when I pull my 12000 lb fiver?"

It will act the same, the weight of the trailer doesn't matter. Its Engine temp related. Dont worry about it.

Its your fan clutch.

You stated....
"Maybe this is normal but if it does this pulling 7000 lbs. what's it going to sound like when I pull my 12000 lb fiver?"

It will act the same, the weight of the trailer doesn't matter. Its Engine temp related. Dont worry about it.

:exactly: Nothing to worry about - Enjoy your ride!

Man I can't believe how fast you guys responded. Yes it was hot, about 95, and I thought it might have been the fan but I was surprised that it was louder than the engine. Actually drowned out the engine noise. Well thanks for putting my fears to rest.

shocked the sh-t out of me when mine did it the first time. It was a couple days ago it was hot out and the truck had been idling at a red light for a couple minutes so I figured it was an aux fan. Nice to have it confirmed!!

So what do you do about the fan in this situation?

It's the normal operation of the fan, there isn't anything to do.

Wait till it gets cold. You think it makes strange noises now. :exactly:

Stu it doesn't get cold where I live. :) :D

That's too bad, I love the cold and the snow (See signature for why :D )

I had my DMax in the U.P. of Michigan in late January this year. Truck sat for 3 days without being started. Highest temp was around 15 to 20 Ferenheit during the day and at or below 0 at night. Hooked up the heater for about 20 mins before we left and she started right up. Thank you synthetic oil and fuel treatment. She did make some interesting noises for the first few minutes she ran, but once she was warmed up it ran like a charm.

That's too bad, I love the cold and the snow (See signature for why :D )

I had my DMax in the U.P. of Michigan in late January this year. Truck sat for 3 days without being started. Highest temp was around 15 to 20 Ferenheit during the day and at or below 0 at night. Hooked up the heater for about 20 mins before we left and she started right up. Thank you synthetic oil and fuel treatment. She did make some interesting noises for the first few minutes she ran, but once she was warmed up it ran like a charm.


Don't forget props to your good friends Mr. and Mrs Batteries and also Mr. Antifreeze :ro)

is this at a particular rpm or just specific gears? My 05 duramax/allison has an annoyingly loud hum at 1700-1800 rpm in any gear. After that range or before it sounds great.

That sound is a hum coming from your exhaust pipe resonating. Read the thread I am posting for you, print it out, and go tell your service department to apply the fix.

http://www.dieselplace.com/forum/showthread.php?t=24776

cya!

.