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Discussion Starter #1
Hello,

I have a very intermittent problem.

Every week or so, after startup there is a grunch noise, kind like a starter not releasing. Here is the interesting part.

the noise happens after the engine RPM comes down to idle. So it will start, and upon start up have slightly elevated RPM's, they will go down to regular idle, then the grunch happens.

ideas? Dealer is useless as there is no code....and it will nver do it when I am there.....

oh, 2007 6.7 3500 4 x 4 auto.
 

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Mine also makes the "grrrrrunnnnch" sound, on startup, sometimes.
 

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I have the same sound. I was wondering how to put that into words. But I think "Grunch" will do for now. Can you imagine trying to tell the service manager about that noise under the hood. Talk about a deer in the head light stare. lol very good.
 

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Smells like Bananas
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Turn your A/C off before you start it up. After the truck is running and if you have not heard that sound turn the A/C on to see if that sound yall here is it coming on. Whether the A/C is on or not at start up it does not come on until the engine has been running for a few secs.
 

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I've heard the same "grunch" sound three times now. Two of the times, it happened a few seconds after start up. The third time, it happened after I started it up, backed up, and started taking off. I always turn off my a/c before shutting the motor down, so the a/c was off everytime I heard that noise. Seems to run just fine afterwards, but I'm clueless to what it could be. :kick:
 

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My AC makes this "grunch" sound when it's turned on. Not every time but many.
 

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Discussion Starter #9
So far so good - Fan turned to off every day. I will update as time progresses.
 

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TECH SPECIALIST
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it is your A/C compressor kicking in to stop it have the a/c compressor off when you start the truck and wait a min or two to turn it on
 

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I ran a little test on mine the past 2 days. I deliberately set the A/C to be on with the fan switch on and tried to get mine to make the sound. Mine is quiet, so I'd say the noise isn't normal.
 

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Maby amaco transmission can tell what the noise is :rof Remember the commercials they had :rof
 

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Grunch!!! Now the sound has an official name. :D

It has only happened twice in 3000 miles for me, once I think it was the A/C starting and the other time it sounded more like the VGT in the turbo cycling closed for a second.
 

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mine makes that grunch noise also, sounded like the ac to me,but i'm not sure.i'ts done it 4 or 5 times in the first 5000 miles.
 

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Mine too

Mine does that as well, every 10 or so startups.

Had it happen last night, EB was off and AC was off. Occurs approx 3 seconds after startup, you can hear a noise that sounds like a mechanical sliding noise then "crunch".

I engage my EB and drive around till operating temps are normal, so the turbo shouldn't be sooted up, but we'll see.

Going to the dealer tomorrow for an oil change and will report this, no codes so unless STAR has a recommendation, not much is going to happen.

Almost at 5K miles.
 

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Got a case of the Grunch!

Got the same problem, only hear the sound at startup and only every 10 - 15 startups.
Took me a while to find a match using the search but Grunch is the best way to describe this sound! :hehe:
 

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knew an old guy yrs back named Grunch can't remember the sound he made!!!!!!!!
 

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Just a little reminder here. When testing, not only should you have the A/C switch off, but also make sure the heat selector is NOT set to a defrost setting. When you select defrost, the A/C kicks in as well -- this helps dry the air and defog the windows that much faster.
 

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Mine has done it twice now. Both times I was just a hundred feet or so past the driveway, and turning on the a/c. The last time it happened, I just happened to be driving past the dealer, so I had them check it out. I described it as a "gear clashing" type noise that sounded like the turbo or the a/c compressor.

The dealer checked the codes (none), and said to let them know if it keeps happening.

The stop wasn't all bad though, I had them enable my HIGH IDLE when I was there.

I just remembered: The last time it happened, it SEEMED like whatever happened robbed power from the engine for a second. It COULD have been my imagination, but I was accelerating, and it seemed to slow during the noise.
 
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