2004.5-2005 GM 2500HD/3500HD 6.6L LL Duramax Engine & Performance

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2004.5-2005 6.6L Silverado & Sierra 2500HD/3500HD

2004.5-2005 GM 2500HD/3500HD 6.6L LLY Duramax Crate Engines

Crate Engines

2004.5-2005 GM 2500HD/3500HD 6.6L LLY Duramax Gaskets, Gasket Kits & Bearings

Gaskets

2004.5-2005 GM 2500HD/3500HD 6.6L LLY Duramax Glow Plugs

Glow Plugs

2004.5-2005 GM 2500HD/3500HD 6.6L LLY Duramax Head Studs & Main Studs

Head Studs & Main Studs

2004.5-2005 GM 2500HD/3500HD 6.6L LLY Duramax Heads & Valve Train

Heads & Valve Train

2004.5-2005 GM 2500HD/3500HD 6.6L LLY Duramax Motor Mounts

Motor Mounts

2004.5-2005 GM 2500HD/3500HD 6.6L LLY Duramax Oil Pans

Oil Pans

2004.5-2005 GM 2500HD/3500HD 6.6L LLY Duramax Radiators & Cooling Upgrades

Radiators & Cooling Upgrades

2004.5-2005 GM 2500HD/3500HD 6.6L LLY Duramax Rebuild Kits & Internal Parts

Rebuild Kits & Internal Parts

2004.5-2005 GM 2500HD/3500HD 6.6L LLY Duramax Rods, Pistons, Cams & More

Rods/Pistons/Cams & More

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$15,400
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Wehrli 100155 Billet Coolant Heater Core Firewall Fitting | 1999-2025 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Wehrli 100155 Billet Coolant Heater Core Firewall Fitting | 1999-2025 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Wehrli 100155 Billet Coolant Heater Core Firewall Fitting | 1999-2025 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Wehrli Custom Fab

Wehrli 100155 Billet Coolant Heater Core Firewall Fitting | 1999-2025 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

$39.77
ARP 230-5401 Main Stud Kit | 2001-2005 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
ARP 230-5401 Main Stud Kit | 2001-2005 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

ARP

ARP 230-5401 Main Stud Kit | 2001-2005 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

$241.65
$460.91
Merchant 10479 Exhaust Manifold to Cylinder Head Bolt Kit | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Merchant 10479 Exhaust Manifold to Cylinder Head Bolt Kit | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Merchant Automotive

Merchant 10479 Exhaust Manifold to Cylinder Head Bolt Kit | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

$79.72
Mahle 54582 Right Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Mahle 54582 Right Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Mahle

Mahle 54582 Right Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

$86.34
$184.19
PPE 114000555 MicroPure Extreme Performance Engine Oil Filter | 2001-2019 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
5.0
PPE 114000555 MicroPure Extreme Performance Engine Oil Filter | 2001-2019 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
PPE 114000555 MicroPure Extreme Performance Engine Oil Filter | 2001-2019 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
PPE 114000555 MicroPure Extreme Performance Engine Oil Filter | 2001-2019 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

PPE

PPE 114000555 MicroPure Extreme Performance Engine Oil Filter | 2001-2019 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

$35.99
Mahle CS54580 Lower Engine Gasket Kit | 2001-2007 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Mahle CS54580 Lower Engine Gasket Kit | 2001-2007 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Mahle

Mahle CS54580 Lower Engine Gasket Kit | 2001-2007 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

$132.67
$299.37
EFI Live FS3-GM-DC Flashscan V3 | And RAM Tuning
EFI Live FS3-GM-DC Flashscan V3 | And RAM Tuning

EFI Live

EFI Live FS3-GM-DC Flashscan V3 | And RAM Tuning

$1,425
Mahle 54585 Left Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Mahle 54585 Left Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Mahle

Mahle 54585 Left Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

$99.23
$190.89
EFI Live FS3-GM Flashscan V3 | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
EFI Live FS3-GM Flashscan V3 | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

EFI Live

EFI Live FS3-GM Flashscan V3 | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

$1,025
PPE 114003000 Billet Aluminum Engine Oil Filler Cap | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
PPE 114003000 Billet Aluminum Engine Oil Filler Cap | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
PPE 114003000 Billet Aluminum Engine Oil Filler Cap | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
PPE 114003000 Billet Aluminum Engine Oil Filler Cap | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
PPE 114003000 Billet Aluminum Engine Oil Filler Cap | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

PPE

PPE 114003000 Billet Aluminum Engine Oil Filler Cap | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

$31.49
Merchant 19210615 Engine Oil Cooler Assembly | 2001-2010 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Merchant 19210615 Engine Oil Cooler Assembly | 2001-2010 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Merchant 19210615 Engine Oil Cooler Assembly | 2001-2010 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Merchant Automotive

Merchant 19210615 Engine Oil Cooler Assembly | 2001-2010 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

$799.73
Edge 85401-201 Evolution CTS3 50 State Legal Programmer | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Edge 85401-201 Evolution CTS3 50 State Legal Programmer | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Edge 85401-201 Evolution CTS3 50 State Legal Programmer | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Edge 85401-201 Evolution CTS3 50 State Legal Programmer | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Edge 85401-201 Evolution CTS3 50 State Legal Programmer | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Edge Products

Edge 85401-201 Evolution CTS3 50 State Legal Programmer | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

$689.95

2004.5-2005 6.6L Silverado & Sierra 2500HD/3500HD

Power Lift Shop All

The 6.6L Duramax LLY under the hood of your 2004.5-2005 GM Sierra/Silverado 2500/3500 may be one of the best and most efficient engines out there, but even the toughest trucks have some power and performance waiting to be unleashed through various performance modifications. Here at Alligator Performance, we carry a selection of cold air intakes, tuners, fuel upgrades, and turbo upgrades to help you get the most out of your diesel engine. Many of these upgrades like the cold air intakes and fuel upgrades even help promote component longevity so you can enjoy long-lasting and consistent performance without compromise. After you've added a few engine upgrades to your custom build, be sure to check out our premium 2004.5-2005 GM 6.6L Duramax LLY Transmission Upgrades to compliment the increase in power you're throwing down! GM Duramax Fitments: 2004, 2005 GM 6.6L Duramax. Submodel Fitments: WT, Custom, LT, LTZ, High Country, 1LT, 2LT, Pro, SLE, SLT, AT4, Denali. Some exceptions apply, please see individual product pages for specific fitments.

GM Duramax>2004.5-2005 6.6L LLY
Tuners & Monitors
Cooling Upgrades
Head Studs & Main Studs
Rods, Pistons & Cams
Heads & Valve Train

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