Attention: If you have a GM Duramax, please verify your engine type before ordering any product. Many of the products we offer are not interchangeable with all Duramax engine types. To Verify: Check the 8th digit in the VIN number:
VIN Code 1 – LB7 (2001-2004)
VIN Code 2 – LLY (2004.5-2006)
VIN Code D – LBZ (2006-2007)
VIN Code 6 – LMM (2007.5-2010)
VIN Code 8 – LML (2011-2016)
Halfway through the 2004 model year, the second generation of the Duramax diesel engine was introduced in GM Silverado/Sierra 2500HD/3500HD pickups. Since the LLY and LB7 engines were both available in the same year, the LLY was unofficially referred to as the 2004.5 model year by the diesel aftermarket and enthusiasts alike. The second generation 6.6L Duramax continued to utilize several components from the first generation Duramax, but also included new components that increased performance. A new variable-vane turbocharger and was the key improvements to this engine. The previous generation Duramax engine was plagued with injector failures which led to the revision of the common-rail fuel system for the 2004.5 Duramax. GM designed this engine to provide durability and reliability in their heavy-duty pickups.
One of the main elements that was carried over from the LB7 Duramax to the LLY was the solid deep-skirt engine block foundation. The 6.6L Duramax LLY engine block was cast in a gray iron alloy and fitted with cast-aluminum heads. This engine featured an overhead valve (OHV) design with 4 valves per cylinder, for a total of 32 valves. For added durability, this Duramax engine contained cast-aluminum pistons and forged-steel connecting rods with a cracked cap design. A high-pressure common-rail fuel system powered by a Bosch CP3 injection pump would continue to be utilized on the LLY engine. To avoid similar injector issues from the first generation Duramax, new externally serviceable fuel injectors were added.
Another upgrade from the first generation Duramax was the new variable-vane turbocharger. This Garret GT3788VA turbocharger featured a 62mm compressor wheel making it the largest flowing factory turbocharger on a Duramax engine. The VVT style turbocharger also provided better throttle response throughout the RPM range. Between 2004.5-2005 the Duramax LLY was rated at 310 hp and 520 lb-ft of torque. Paired with this Duramax engine was either a ZF 6-speed manual transmission or a heavy-duty 5-speed automatic Allison transmission. Parts for GM Silverado/Sierra 2500HD/3500HD trucks powered by the Duramax LLY are still readily available. Whether you’re looking to do routine maintenance or boost horsepower and torque in your Duramax, Cyberpunk Diesel has what you need. From simple maintenance such as an oil change or bigger projects including replacing a Head Gasket, Cyberpunk Diesel has you covered. Shop hundreds of the top manufacturers for diesel performance parts including Fuel Lift Pumps, Performance Injectors, or Turbo Upgrades. Cyberpunk Diesel has the parts your 2004.5-2005 GM 6.6L Duramax LLY needs.
