L5P tapping/knocking noise when coasting???

[email protected]

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The knocking where they advanced the timing that is how they made the extra HP for the engine as of right now they have no fix for it asked a tech at the dealership yesterday

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IOWA LLY

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Feb 23, 2007
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The knocking where they advanced the timing that is how they made the extra HP for the engine as of right now they have no fix for it asked a tech at the dealership yesterday

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That tech is full of shit


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DangerousDuramax

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Nov 3, 2006
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That tech is full of shit


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Dang, all it takes to gain 50hp and 100+ lb-ft is a bump in timing? :roflmao:
LOL! What THEY said!!! :roflmao: So the timing anomaly during DECELERATION is what gives a power increase???!!! REALLY??!!! HORSEPOWER INCREASES AT 0% THROTTLE POSITION???!!! :roflmao::roflmao::roflmao: STOP LISTENING TO DUMBASS TECHS AT THE DEALERSHIP WHO ARE PAID TO BLOW SMOKE UP YOUR ASS TO PROTECT THE DEALERSHIP FROM WARRANTY CLAIMS!!!! :thumb:
 

Duvel

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I'm still waiting on a reply from my dealership on what the reasoning is. I've seen the emails they sent out requesting information, but GM is being tight lipped about it.
 

gl4787

<-- just sits
Jan 27, 2009
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LOL! What THEY said!!! :roflmao: So the timing anomaly during DECELERATION is what gives a power increase???!!! REALLY??!!! HORSEPOWER INCREASES AT 0% THROTTLE POSITION???!!! :roflmao::roflmao::roflmao: STOP LISTENING TO DUMBASS TECHS AT THE DEALERSHIP WHO ARE PAID TO BLOW SMOKE UP YOUR ASS TO PROTECT THE DEALERSHIP FROM WARRANTY CLAIMS!!!! :thumb:
True said tech is full of it but why would you think a tech wouldn't want to do a warranty claim? You do realize that the service director, manager, writer and tech all make money off of warranty claims right? It's like doing work to a vehicle that you don't have to get a customer to pay for. Not trying to bash just trying to see your logic in that statement. Only reason it hits a nerve with me is because these are the kinds of things I hear from customer's all the time. "The dealer just doesn't want to fix my car for free so they're going to wait until I'm out of warranty".
 

gl4787

<-- just sits
Jan 27, 2009
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I'm still waiting on a reply from my dealership on what the reasoning is. I've seen the emails they sent out requesting information, but GM is being tight lipped about it.
Did they contact their District Service & Parts Manager (DSPM)? He/she is really the only one that would be able to produce a real answer to this kind of question because they're really the only one's that get their answers straight from GM.
 

DangerousDuramax

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True said tech is full of it but why would you think a tech wouldn't want to do a warranty claim? You do realize that the service director, manager, writer and tech all make money off of warranty claims right? It's like doing work to a vehicle that you don't have to get a customer to pay for. Not trying to bash just trying to see your logic in that statement. Only reason it hits a nerve with me is because these are the kinds of things I hear from customer's all the time. "The dealer just doesn't want to fix my car for free so they're going to wait until I'm out of warranty".
Dealerships avoid warranty claims if at all possible. We all know this...its nothing new. They get screwed many times because of fraudulent or incorrect warranty claims. My statement is directed at a tech trying to keep the dealership from suffering an unnecessary warranty claim over something that only exists in the customers mind and isn't an actual problem with the truck. GM programmed the timing anomaly into the Duramax and now that some customers have caught wind of it they will be at the dealerships door knocking saying "something is wrong with my truck please fix it for free" when there isn't any problem. GM isn't going to tell anyone why they did it or what its for. That tech now has to waste his time on a problem that doesn't exist and wont make the dealership a single dime. In fact...its now costing the dealership money for that tech to chase a problem that doesn't exist while he could've been working on an actual real problem that will make the dealership money. Time = money. Wasted time = lost or wasted money.
 

gl4787

<-- just sits
Jan 27, 2009
274
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WI
Dealerships avoid warranty claims if at all possible. We all know this...its nothing new. They get screwed many times because of fraudulent or incorrect warranty claims. My statement is directed at a tech trying to keep the dealership from suffering an unnecessary warranty claim over something that only exists in the customers mind and isn't an actual problem with the truck. GM programmed the timing anomaly into the Duramax and now that some customers have caught wind of it they will be at the dealerships door knocking saying "something is wrong with my truck please fix it for free" when there isn't any problem. GM isn't going to tell anyone why they did it or what its for. That tech now has to waste his time on a problem that doesn't exist and wont make the dealership a single dime. In fact...its now costing the dealership money for that tech to chase a problem that doesn't exist while he could've been working on an actual real problem that will make the dealership money. Time = money. Wasted time = lost or wasted money.
I guess I can see where you're correct to a certain extent, however, I've made a lot of money over the years on warranty work at a dealership and to say that warranty work is avoided if at all possible is 100% incorrect. As a matter of fact I regularly do warranty repairs on vehicle's that are found on inspection that a customer would have never even know about if I had never found.
 

THEFERMANATOR

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Feb 16, 2009
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I'm still going to venture it was done to control cylinder imbalance to reduce crank stress. It's not an issue, but the engine is quiet in so many other regards, that this non issue has become an issue because it doesn't fit in with the other sounds of the engine. I know this knocking on decel has been there since day 1 as my LB7 did it, but it was a more uniform noise as all cylinder were at the same timing. It just wasn't noticeable to most as the noise fit in with the other noises. People are now expecting gas engine quietness from a diesel under all circumstances. I'm curious to see if any crank failures come of it if/when the aftermarket "FIXXES" this noise with tuning?
 

Mark06

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Feb 15, 2017
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I've heard the 2017 Ford F series 6.7L Diesel and it doesn't make any acceleration or deceleration knocking sounds. This sound might be due to the slower response time of the new solenoid injectors GM is now using.
 

[email protected]

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Jan 8, 2017
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Not only is mine making the knocking. I had my windows down turning into a parking lot and the front end was making a popping noise took it to the dealership and they found a nut loose on the axle they tighten it up but still doing it so they are replacing the front axles


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IOWA LLY

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Feb 23, 2007
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I'm still going to venture it was done to control cylinder imbalance to reduce crank stress. It's not an issue, but the engine is quiet in so many other regards, that this non issue has become an issue because it doesn't fit in with the other sounds of the engine. I know this knocking on decel has been there since day 1 as my LB7 did it, but it was a more uniform noise as all cylinder were at the same timing. It just wasn't noticeable to most as the noise fit in with the other noises. People are now expecting gas engine quietness from a diesel under all circumstances. I'm curious to see if any crank failures come of it if/when the aftermarket "FIXXES" this noise with tuning?


How is timing at 0% throttle, with virtually no fuel, and no load, going to hurt, or help the crank?



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THEFERMANATOR

LEGALLY INSANE
Feb 16, 2009
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How is timing at 0% throttle, with virtually no fuel, and no load, going to hurt, or help the crank?



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The pilot pulse can fuel upwards of 8mm3 of fuel IIRC from looking at other tune files. Seems to me MANY have had crank failures just cruising along, let off the throttle, and bam it happens. Maybe GM is on to something we don't know about with it, maybe not. I know I'm not the only person who has said even in thos thread, that the "fix" could cause issues. Unless they put a cylinder pressure monitor in the engine when they make the change, nobody will know what it will do.
 

2004LB7

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Dec 15, 2010
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Is it possible it is for some kind of engine breaking? Early combustion to resist the pistons coming up thus slowing the engine
 

dmaxerLLY

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Ticking noise is definitely there, only when coasting from the top of a gear. RPM has to be up prior to lifting for the knock to sound. Shift strategy is sorta weird compared to my lmm, overall it feels solid but it needs a tune up in the performance department, granted it is a 3500 dually its no slouch.
 

RPM Motorsports

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May 13, 2008
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Down shift strategy is definitely odd haha. I find myself looking to see if I accidentally turned tow haul on. The decel "tow haul" style down shifting would prob net better fuel mileage, if it was like we were used to on the older models. Seems like once it goes 2/1, 1st gear is normal and neutral. Guess that's my only complaint, I like the coasting/neutral down shift compared to the new Exhaust brake feel of the new truck (yes it's off ;) )
 

chevyburnout1

Fixing it till it breaks
Aug 25, 2008
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The pilot pulse can fuel upwards of 8mm3 of fuel IIRC from looking at other tune files. Seems to me MANY have had crank failures just cruising along, let off the throttle, and bam it happens. Maybe GM is on to something we don't know about with it, maybe not. I know I'm not the only person who has said even in thos thread, that the "fix" could cause issues. Unless they put a cylinder pressure monitor in the engine when they make the change, nobody will know what it will do.
I'm truthfully surprised with what all is going on in that cylinder that GM hasn't implement cylinder pressure sensors like in the Volkswagen TDI's. I never realized this was a factory thing until I got a check engine light for one.
 

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