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6.6L LLY Duramax Specifications & Information

6.6L LLY Duramax Specs

LLY Duramax Specs & Background

The 2nd generation Duramax is known as the LLY. Similar to the LB7, the LLY Duramax is reliable, powerful, and lacks most of the emissions found on modern day diesel trucks like the L5P. LLY Duramax trucks don’t suffer from the same injector failure problems that LB7 trucks frequently had. Instead, many LLY Duramax problems stem from overheating. A new variable vane turbocharger and an EGR system were also added. Check out our LLY Duramax Specifications chart below for detailed information!

6.6L LLY Duramax
6.6L LLY Duramax

The LLY Duramax was produced from 2004 to 2006, before it was eventually replaced by the LBZ Duramax. It was a stepping stone for GM as they begun to encounter stricter emissions requirements thanks to the federal government and California. Despite the added emissions, the LLY was very powerful and capable for the time producing 310 horsepower and 605 lb/ft of torque. It was mated to a 5-speed Allison Transmission in years 2004 and 2005. In 2006, the Allison Transmission was upgraded to a 6 speed.

LLY Duramax Specifications Chart

Manufactured Years:2004-2006
Engine Design: 6.6L 90-Degree V8 Turbocharged Diesel
Transmission:2004-2005: 5-Speed Auto Allison Transmission
2006: 6-Speed Auto Allison Transmission
Vin Identification:
(8th Digit)
Displacement:6.6 Liters or 403 Cubic Inches
Engine Weight:835 Lbs
Bore:4.055″ or 103 mm
Stroke:3.897″ or 99 mm
Block Material:Cast Iron
Cylinder Head:Cast Aluminum
Crankshaft:Forged Steel
Connecting Rods:Forged Steel
Compression Ratio:17.5:1 (2004 & 2005)
16.8:1 (2006)
Firing Order:1-2-7-8-4-5-6-3
Turbocharger And Intercooler
Fuel Injection:Direct Injection High Pressure Common Rail
with Bosch CP3 Injection Pump
Valvetrain:Overhead Valve (OHV) 4 Valves per cylinder (32V)
Engine Oil Capacity:10 Quarts With Filter
Fuel Tank Size:Short Beds: 26 Gallons
Long Beds: 34 Gallons
Max Engine Speed:3,250 RPM
Horsepower:310 horsepower
Torque:2004 & 2005: 520 lb/ft @ 1,600 rpms
2006: 605 lb/ft @ 1,600 rpms

LLY Duramax Performance

Although our LLY Duramax specifications chart above does mention the turbocharger found on these trucks, it doesn’t mention the fact that these are one of the largest turbochargers found on any Duramax today. While this makes adding extra horsepower and torque super easy, it also makes the LLY Duramax more susceptible to head gasket failure. Be careful if you decide to tune your LLY with EFI Live or another tuner. You should consider investing in a head stud kit from ARP! If you want to upgrade your LLY’s performance, check out our favorite performance upgrades for an LLY Duramax post.

LLY Problems

Although the injector issues of the LB7 Duramax didn’t carry over to the LLY, the second generation Duramax still has its fair share of problems. Just like the LB7, no lift pumps were included on these trucks stock. An aftermarket lift pump like a Fass or Air Dog should be one of the first upgrades you consider. It’ll give you plenty of fuel and it’ll offer much better fuel filtration than your stock fuel filter. This will help preserve important and expensive parts like your fuel injection pump and fuel injectors.

LLY Duramax trucks have been known for overheating issues. Factory design issues like a small radiator with less coolant capacity and restrictive air flow make these trucks run hot! We go into more detail on our LLY Duramax problems page.

Like other Duramax trucks, if you have an LLY Duramax you’re going to want to beef up your front end. Want to add bigger tires or bigger wheel? While the independent front suspension, or IFS suspension, provides a very comfortable ride, it’s not nearly as stout as a straight axle. There are several products you can get to upgrade your front end. I always buy Kryptonite or Cognito front end parts for my Duramax trucks. I’ve included some links to my favorite parts below.

LLY Duramax Tow Capacity

The LLY Duramax was sold from 2004-2006 and tow capacity varies between model years. Conventional tow capacity across all models is 12,000 lbs. 5th Wheel tow capacity varies between years and depends on cab configuration. Numbers generally fall between 15,000 lbs and 16,700 lbs though. Duallies and two-wheel drive models also offer higher tow ratings. Larger cabs and 4wd models offer less 5th wheel tow capacity. Check out our complete Duramax tow ratings guide for detailed towing specifications!

Learn More About The LLY Duramax

Check out some of our other resources for LLY Duramax owners! Click on one of the links below or in the side bar for more information.

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