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Just what the title says. 2004 duramax clunk in drivetrain under nuetral power. I have no idea where to begin, just bought it. LLY, Allison, 4WD.

Thank you all!!! I have been a lurker for a while.

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Just what the title says. 2004 duramax clunk in drivetrain under nuetral power. I have no idea where to begin, just bought it. LLY, Allison, 4WD.

Thank you all!!! I have been a lurker for a while.

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You might have pump rub in the t-case I’d start by checking ur u-joints though and try twisting the drive shaft in park on level ground


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I had a clunk in my 2002 2WD for years. It was especially bad in hot weather. Most noticeable: at a stop light, in drive with foot on the brake. Light turns green, let foot off brake and before you can even touch the gas pedal, there is a loud clunk that is heard and felt. Truck did this almost since new and a few years ago another long-time owner of a 2002 suggested that I try greasing the drive shaft yoke with Red & Tacky. Figure what the heck, nothing to lose so I did it. Boom, problem solved.
 

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@long-time-dmax Arent the yokes lubed by trans fluid and wouldnt the grease be diluted and eaten up by the trans fluid even if we did grease it?
 

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What do you mean “under neutral power”? Are you saying that if you have the truck stationary, transmission in neutral, and increase the engine speed, you then have a noise?
 

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Discussion Starter #9
What do you mean “under neutral power”? Are you saying that if you have the truck stationary, transmission in neutral, and increase the engine speed, you then have a noise?
Not accelerating, but not deceleration, hold the throttle slightly to maintain speed, most common around 30-40 mph.


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Not accelerating, but not deceleration, hold the throttle slightly to maintain speed, most common around 30-40 mph.


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Is this a rotational noise or only one that you notice with driveline load changes (power to coast and vice versa) ?
 

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It is a rotational noise, like a kitchen aid blender fill with bolts on speed number 5, lol. Lasts for a second at a time. I can throw a gopro under the truck if it would help.
 

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@long-time-dmax Arent the yokes lubed by trans fluid and wouldnt the grease be diluted and eaten up by the trans fluid even if we did grease it?

Sorry, left out crucial details... I lubed the slip yoke between the 2 drive shafts (2 piece drive shaft).
 

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It is a rotational noise, like a kitchen aid blender fill with bolts on speed number 5, lol. Lasts for a second at a time. I can throw a gopro under the truck if it would help.
Any difference if the transfer case is in 4WD? If not, and if you feel safe doing it, get the rear axle up on jackstands and try to recreate the noise by running the truck on jack stands so that you can get underneath it so that you can get a better location on the noise.
 

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Any difference if the transfer case is in 4WD? If not, and if you feel safe doing it, get the rear axle up on jackstands and try to recreate the noise by running the truck on jack stands so that you can get underneath it so that you can get a better location on the noise.
God call, that is my next step... I will chime in Sunday with results...


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Sorry, left out crucial details... I lubed the slip yoke between the 2 drive shafts (2 piece drive shaft).
Ahhh Ok. I guess i am one of the fortunate ones? I have a one piece. BTW what determines getting a one piece or a two piece driveline from the factory? Did they start putting one piece in our trucks trucks after a certain year? Meaning 01 - 04 LB7s.
 

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Ahhh Ok. I guess i am one of the fortunate ones? I have a one piece. BTW what determines getting a one piece or a two piece driveline from the factory? Did they start putting one piece in our trucks trucks after a certain year? Meaning 01 - 04 LB7s.
Drivetrain options - 2WD to 4WD
and
Wheel base options - cab and bed sizes.

That’s what determines 1 or 2 piece driveshaft.
 

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Drivetrain options - 2WD to 4WD
and
Wheel base options - cab and bed sizes.

That’s what determines 1 or 2 piece driveshaft.

Ok cool. I like my One piece, less moving parts.

Thanks for the info. I had no idea

Couldnt the clunk in Henry165s truck be the shifting fork. Mine went out and it sounded like a bucket of bolts. In what he is describing. Just a question
 
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