HomeBlogGuestThe Duramax LB7, LLY, LBZ, LMM and LML Remanufactured Diesel Engines Are Available at Roadmaster Engine World.
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The Duramax LB7, LLY, LBZ, LMM and LML Remanufactured Diesel Engines Are Available at Roadmaster Engine World.

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The Duramax LB7, LLY, LBZ, LMM and LML remanufactured diesel engines are available at Roadmaster Engine World.

The Duramax is a General Motors diesel engine family for light- and medium duty trucks, designed by Isuzu. The 6.6-liter Duramax is produced by DMAX, a joint venture between GM and Isuzu in Moraine, Ohio. This engine was initially installed in 2001 model year Chevy and GMC trucks and has been an option since then in pickups, vans, and medium-duty trucks. In 2006, production at Moraine was reportedly limited to approximately 200,000 engines per year. On May 9, 2007, DMAX announced the production of the 1,000,000th Duramax V-8 diesel at its Moraine facility.


RPO LB7 (engine code "1") was first introduced in 2001 and continued until mid 2004. It is a 32-valve design with high-pressure common-rail direct injection and an experimental composite design cylinder head. The most problematic issue with the LB7 is injector failure. Fuel leaked and entered the crankcase, causing oil dilution. Early on, customers came forward complaining of severe overheating, and in some situations, blown head gaskets. Initially GM denied it was a problem, but after being sued by a consumer group, GM relented and included overheating and blown head gaskets as a warranted item. GM issued a warranty for this after the fact for injectors, which now have 7 year/200,000 mile coverage. The following trucks use the LB7:

  • Chevrolet Kodiak/GMC Topkick
  • Chevrolet Silverado/GMC Sierra HD


The LLY (internally called the 8GF1) (engine code "2") is a 6,599 cc (402.7 cu in) turbocharged engine which debuted in mid-2004 and continued until the end of 2005. It is a 32-valve design with high-pressure common-rail direct injection and aluminum cylinder heads. The LLY was GM's first attempt to implement emissions requirements on their diesel trucks. To meet this goal they turned to a newly developed Garrett turbocharger with a variable geometry vane system and they installed an Exhaust Gas Recirculation valve or (EGR Valve). Learning from problems with injectors in the previous LB7 GM changed the valve covers to allow access to the injectors without having to remove the valve covers, saving significant labor costs if injector replacement became necessary.

The following trucks used the LLY engine:

  • 2006 Hummer H1 Alpha
  • Chevrolet Silverado/GMC Sierra HD


The 2006 LLY (engine code "2") debuted in the beginning of 2006 and ended production with the start of the 2007 calendar year. Mechanically it is identical to the LBZ and is mated to the new 6-speed Allison transmission however it retained the LLY designation.

The LBZ (engine code "D") debuted in late 2006 and continued into 2007 sold only in the "classic" body style. It has a more powerful tune loaded into the computer that allows it to produce more power and torque.

Changes include:

  • Cylinder block casting and machining changes strengthen the bottom of the cylinder bores to support increased power and torque
  • Upgraded main bearing material increases durability
  • Revised piston design helps lower compression ratio to 16.8:1 from 17.5:1
  • Piston pin bore diameter increased for increased strength
  • Connecting rod " I " section is thicker for increased strength
  • Cylinder heads revised to accommodate lower compression and reduced cylinder firing pressure
  • Maximum injection pressure increased from 23,000 psi (1,585.8 bar) to more than 26,000 psi (1,792.6 bar)
  • Fuel delivered via higher-pressure pump, fuel rails, distribution lines and all-new, seven-hole fuel injectors
  • Fuel injectors spray directly onto glow plugs, providing faster, better-quality starts and more complete cold-start combustion for reduced emissions
  • Improved glow plugs heat up faster through an independent controller
  • Revised variable-geometry turbocharger is aerodynamically more efficient to help deliver smooth and immediate response and lower emissions
  • Air induction system re-tuned to enhance quietness
  • EGR has larger cooler to bring more exhaust into the system
  • First application of new, 32-bit E35 controller, which adjusts and compensates for the fuel flow to bolster efficiency and reduce emissions"

LBZ applications:

  • Chevrolet Silverado HD
  • Chevrolet Kodiak
  • GMC Sierra HD
  • GMC TopKick

LLY applications:

  • Chevrolet Silverado HD
  • Chevrolet Kodiak
  • GMC Sierra HD
  • Chevrolet Express full-size (reduced power output mated to a 4L85E transmission)
  • GMC Savana full-size (reduced power output mated to a 4L85E transmission)


The LMM (engine code "6") debuted part way through 2007 and ended production with the start of the 2011 calendar year and is mated to the 6-speed Allison transmission. The LMM was the only Duramax offered for model years 2008-2010.

(Diesel Oxidizing Catalyst) where the fuel is burned to elevate the temperature of the exhaust. This hot exhaust flows into the DPF and burns the trapped soot.

Emission controls:

  • Additional combustion control, including an even more efficient variable-geometry turbocharging system, cooled (enhanced) exhaust gas recirculation (EGR) and closed crankcase ventilation to reduce nitrogen oxides (NOx)
  • Additional exhaust control, including oxidizing catalyst and new diesel particulate filter (DPF) to reduce soot and particulate matter
  • Increased-capacity cooling system
  • New engine control software
  • Use of low-ash engine oil (CJ-4)


  • 2007- Chevrolet Silverado HD[8]
  • 2007- GMC Sierra HD
  • Chevrolet Kodiak
  • GMC Topkick
  • Chevrolet Express/GMC Savanna


The 6.6L RPO LML (VIN code "8") is the latest version (2011-present) of the Isuzu/GM Duramax V8 diesel engine and actually a further advanced version of the LMM engine with the majority of the changes addressing a required drastic reduction in engine emissions. Some mechanical aspects of the engine, such as piston oil flow design for improved temperature control and oil pump design, were also improved to enhance durability even further.

The LML engine was significantly updated for 2011 to provide improved exhaust emissions that comply with the new federal emission standards for diesel engines, provide better engine rigidity and further noise reduction. New 29,000 PSI piezo injectors, a complete fuel system-hardening to tolerate up to 20% biodiesel mixtures and urea injection (to reduce Nitrogen oxides) with a 5.3 gallon urea tank are updating the fuel and emissions systems. This engine has a fuel injector in the exhaust tract, to allow raw fuel injection during the particulate filter recycling routine. The RPO LML engine is rated at 397 horsepower (296 kW) at 3000 rpm and 765 lb·ft (1,037 N·m) of torque at 1600 rpm.

Roadmaster Engine has been rebuilding diesel engines since 1953.  You can trust that the Chevy Duramax rebuilt engine will be the correct engine and one you can depend on.

call us at 800-447-9899 for any additional information you need.

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