well i have pounded on the truck pretty good lately. just some racing and stuff. #2 only and 2wd. tonight i drove about 40 miles down the interstate about 65 and when i got to where i was going i stopped at a stop sign. thats when i noticed this knocking or pecking. the knock is consistent with the way the motor is running. driving down the road or giving the motor a little gas and it disappears. i pulled over to check it out. it wasnt as loud when the truck was in park. i put it back in R or D and it becomes a little louder. so i locked my e-brake and strated snooping around with the truck in gear. i spoke with super diesel and he suggested maybe a cracked flexplate. the sound wasnt really coming from the transmission as much when i held my ear up to it. i inspected the TC through the viewing hole. its hard to explain what i am tryin to say right here but the TC itself didnt have a smooth rotation. what i mean by this is that is looked like it wobbled towards the front and back of the truck. imagine if you drew a line around a cyninder and you made the line perfect all the way around. when you spin it the line looks the same. well in my case the line doesnt run straight. could i have a bolt loose that connects the TC and flexplate. i could really use some help here. if anyone has delt with something similiar and could help me further please call me anytime day or night at 859 514 5127. oh btw i was wonderin if it could be injectors, i havent noticed any smoke but then again i havent been lookin. but the idle is smooth and truck seems to run fine. well thats about all i can think of at the moment. Ryan!http://www.dieselplace.com/forum/images/smilies/help.gif http://www.dieselplace.com/forum/images/smilies/help.gif http://www.dieselplace.com/forum/images/smilies/help.gif
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I've have in fact heard of loose torque converter to flexplate bolts with some of these trucks...

Then again I had a torque converter go out and go out in a bad way in a Jeep and it sounded much like what you describe before it bit the dust. The torque converter bolts in that case were NOT loose.

I N J E C T O R


What are your balance rates when it's knocking?

Does this describe the noise?


Service VME - 6.6L LB7 Duramax Diesel Erratic Tick Noise #PI00040 - (Jun 18, 2002)

6.6L LB7 Duramax Diesel Erratic Tick Noise
SERVICE VME

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

A random ticking noise may be heard in some LB7s with the engine running at idle speed and with the coolant warmed to a temperature of 70 degrees Celsius or above. An Irregular metallic ticking/clacking sound like random typing on a mechanical type writer, can be heard at the lower rear of the left front wheel house. Some customers may also hear the noise inside the cab as well. This irregular ticking/clacking sound can be heard between idle and 1500 rpm. Above 1500 rpm the sound goes away, but returns once the engine is operated within the idle and 1500 rpm speed range.

The sound is caused by the relationship created from the engine block, main bearing crank pin, bearing inser, and oil film which generates a vibration that resonates though the block and is heard as a metallic ticking noise. This noise is most audible on vehicles that have engine main bearing tolerances that are closer to the minimum main bearing clearance specification. All Duramax engines have this condition, however some are more audible than others. Tolerances between nonaudible ticking engines and audible ticking engines are differences in clearances measured in microns.

Isuzu advises that they have experienced this condition in other diesel engines they manufactured over the last 20 years. Other manufactures of diesel engines such as Hino, Mitsubishi and Nissan also report similar noises in their engines. The LB7 bearing manufacturer has investigated this noise in the LB7 and state that no reliability or durability concerns are due to this condition.

General Motors Noise Vibration and Harshness group and Isuzu of Japan Engineering have done extensive testing and agree that no reliability or durability of this engine is effected by this issue. GM engineering has run a ticking engine on a 1200 hour dynamometer durability test and has also agreed that the noise condition does not effect reliability or durability of the LB7 engine.

The noise is a normal operating characteristic of this engine, It has no short term or long term detrimental effects on the engine. Do not attempt repairs for this sound.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.



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mackin, havent been able to get the balance rates checked yet. what does that actually consist of? sorry bout the duplicate thread mackin. i had posted in the other area before it dawned on me to post here. is there a way to delete a thread i start, i know there used to be a way i think but i can find one now.

t-rex i am very well thinkin that its either a loose bolt or a crack in the flex plate

cobra yes the sound is somewhat like that but its actually more evident around the right side(pass) of the vehical. would this noise just appear out of no where? cause in the 12000miles i have had the truck ive never had it until now.

It can, my first dmax didnt do it right away, then the more miles I got, I started to hear it in drive thrus when next to the wall. Eventually it got a little louder, could really only hear it with the window down or when outside the truck. I think it was a little louder on one side, but that was a couple years ago. I dont hear it in the trucks as much as I used to when they first came out though.

kind of like a sharp pop noise, cracking knuckle type sound

hmm wonder why the TC doesnt have a symetrical rotation?

That would cause more of a vibration, if it was out of balance.

well today i couldnt get it to do it, last night it only seemed to do it when i got the truck up to operating temp. im kinda clueless at this point. how hard is it to get one of those balance tests done on the injects? so at least i can start eliminating poss problems

Just hooking up a scan tool and reading the balance rate. Fuel will give you a knock/detonation type noise

I agree with Cobra... especially if the noise fits the symptoms in the bulletin. As for looking at the converter through the inspection hole... illusion. You would have a nasty rpm related vibration if out of balance converter. Balance rates have to be checked with tech 2 and at idle in neutral or park should be similar cylinder to cylinder and not to exceed 4.0. I prefer mine to be less than +- 2.5. Hope this helps.:D