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6.6L Duramax LLY




The Duramax LLY was introduced in 2004 to replace the popular LB7. Like the LB7, the LLY utilizes a high pressure common rail direct injection system. The LLY was General Motors' first attemp at implementing emission controls on a diesel engine to meet stricter emissions requirements in the furture. The LLY adopted a variable geometry turbocharger (VGT) and exhaust gas recirculation (EGR) system to help reduce emissions. Huge changes to the LLY debuted in 2006, but the engines were mechanically identical. LLY's were used in the Hummer H1, Chevrolet Silverado HD, and GMC Sierra HD.



6.6L Duramax LLY Specs


6.6L Duramax LLY, 90 degree V8, diesel.

Years Produced:

2004 - 2006

VIN Code:

2 (8th digit of VIN)


403 cubic inches, 6.6 liters.

Head/Block Material:

Aluminum cylinder heads, cast iron engine block.

Compression Ratio:

17.5 : 1 (2004 & 2005 model years), 16.8 : 1 (2006 model year).

Firing Order:



4.06 inches.


3.90 inches.


Turbocharged and intercooled; Garrett variable geometry turbocharger (VGT), air-to-air intercooler.


Direct injection, 23,000 psi Bosch high pressure common rail with CP3 injection pump.


OHV (overhead valve), 4 valves per cylinder.

Oil Capacity:

10 quarts w/ filter.

Engine Weight:

Approx. 835 lbs.

Max Engine Speed:

3,250 rpm.

Emissions Equipment:

Exhaust gas recirculation (EGR) and diesel oxidation catalyst (DOC).

Peak Horsepower:

310 hp @ 3,000 rpm.

Peak Torque:

• 520 lb-ft @ 1,600 rpm (2004 & 2005 model years).
• 605 lb-ft @ 1,600 rpm (2006 model year).


Additional Duramax LLY Info:

• LLY applications include the Chevrolet Silverado HD, Hummer H1, GMC Sierra HD, Chevrolet Kodiak, GMC Topkick.
• First Duramax to feature emissions controls.
• Cast iron engine block with aluminum cylinder heads.
• 4 bolt mains, forged & fractured connecting rods.
• Aluminum pistons with piston cooling oil jets.
• The LLY was available mated to the Allison 1000 5 speed automatic transmission for 2004 & 2005 model years, and the 6 speed Allison 1000 when it was introduced for the 2006 model year. A ZF 6 speed manual transmission was optional for all model years.
• Produced from 2004 to 2006.