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Ok,
In 2004 GM upgraded the Duramax engine half way through. The change was drastic enough that performance parts such as Intakes and PCM mods for the newer 2004's do not work.

So, how do you know if you have an early 2004(which is called the LB7) or the later 2004 (called the LLY)? Check your vin number. If the 8th digit of your VIN number is a 1, then it is an LB7 Duramax(the early one). If the 8th digit is a 2, then it is an LLY(later 04.5).

Hope this helps!
 

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Hers an up dated list of vin #'s and engines to include the 06 lly and the lbz,

8th Vin #1-LB7 300 hp
8th Vin #2-04.5-05 LLY 310hp autos only, 300 hp manual trans and 4500/5500
8th Vin #3-06 LLY ratings are the same as vin 2
8th vin #D-LBZ 360 hp auto only, not an option in manual trans or 4500/5500 trucks>
 

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So what is the biggest difference between LBY & LLY ?
 

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Injector design...LLY they are a lot easier to change. The turbo is different too. LLY has a Variable Vane Turbo and LB7 has a fixed vane turbo. The LLY was the first to have a cat converter on Federal emissions too.
 

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Does the LB7 not have a cat converter on it?
 

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Some did, california emissions LB7s did come with a cat on them. I don't know if that started before 03 or not. Just crawl under there and see if you have one.
 

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I have a 02 LB7 with 6sp manual trans with 168k and I can't seam to tow a heavy load without it slowing me down considerably when I drive up a slight incline. I don't have a cat and I cut my muffler off and I have a hypertech programmer but I only have it on the 50hp setting for towing. Is there anything else that I can do to get some help out of it, besides a cold air intake?
 

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01, Chevy LB7 here..
 

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Hers an up dated list of vin #'s and engines to include the 06 lly and the lbz,

8th Vin #1-LB7 300 hp
8th Vin #2-04.5-05 LLY 310hp autos only, 300 hp manual trans and 4500/5500
8th Vin #3-06 LLY ratings are the same as vin 2
8th vin #D-LBZ 360 hp auto only, not an option in manual trans or 4500/5500 trucks>
This should be a stickey.
 

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I have an LB7 w/ no cat. I don't care for more restrictions than I am forced to have.
 

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LLY or LB7

The easiest way to tell is if you oil filler cap says "Motor Oil" in french (huile de moteur) it is an LLY. This is directly from the owners manual.:drink
 

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LB7 here
no cat and loving it:drink
 

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01 LB7 no cat, my girl has a 02 LB7 no cat, my buddy has a 04 LB7 with a cat
 

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hahahah bringing it back lol
 
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