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

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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Edge 84130-3 Products Insight CTS3 5 Touch Screen Digital Gauge Monitor | Universal
IN STOCK
Edge 84130-3 Products Insight CTS3 5 Touch Screen Digital Gauge Monitor | Universal
Edge 84130-3 Products Insight CTS3 5 Touch Screen Digital Gauge Monitor | Universal
Edge 84130-3 Products Insight CTS3 5 Touch Screen Digital Gauge Monitor | Universal
Edge 84130-3 Products Insight CTS3 5 Touch Screen Digital Gauge Monitor | Universal
Edge 84130-3 Products Insight CTS3 5 Touch Screen Digital Gauge Monitor | Universal

Edge Products

Edge 84130-3 Products Insight CTS3 5 Touch Screen Digital Gauge Monitor | Universal

SKU: EDG84130-3
$549.95
$618.95
ARP 100-9910 Ultra-Torque Fastener Assembly Lube (10 oz) | Universal
IN STOCK
ARP 100-9910 Ultra-Torque Fastener Assembly Lube (10 oz) | Universal

ARP

ARP 100-9910 Ultra-Torque Fastener Assembly Lube (10 oz) | Universal

SKU: ARP100-9910
$18.13
$34.58
PPE 114000555 MicroPure Extreme Performance Engine Oil Filter | 2001-2019 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
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

SKU: PPE114000555
$35.99
$39.99
ARP 230-4201 Head Stud Kit | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
ARP 230-4201 Head Stud Kit | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
ARP 230-4201 Head Stud Kit | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
ARP 230-4201 Head Stud Kit | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

ARP

ARP 230-4201 Head Stud Kit | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

SKU: ARP230-4201
$640.29
$899.99
Edge 98620 EAS Starter Kit with EGT Cable | Universal
IN STOCK
Edge 98620 EAS Starter Kit with EGT Cable | Universal
Edge 98620 EAS Starter Kit with EGT Cable | Universal

Edge Products

Edge 98620 EAS Starter Kit with EGT Cable | Universal

SKU: EDG98620
$199.95
$224.95
Mahle HS54580A Upper Gasket Kit | 2004.5-2010 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
Mahle HS54580A Upper Gasket Kit | 2004.5-2010 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Mahle

Mahle HS54580A Upper Gasket Kit | 2004.5-2010 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

SKU: MCIHS54580A
$300.72
PPE 119000820 Billet Coolant Block Off Plate | 2001-2026 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
PPE 119000820 Billet Coolant Block Off Plate | 2001-2026 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
PPE 119000820 Billet Coolant Block Off Plate | 2001-2026 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

PPE

PPE 119000820 Billet Coolant Block Off Plate | 2001-2026 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

SKU: PPE119000820
$53.99
$59.99
ARP 100-9911 Ultra-Torque Fastener Assembly Lubricant (20 oz) | Universal
IN STOCK
ARP 100-9911 Ultra-Torque Fastener Assembly Lubricant (20 oz) | Universal
ARP 100-9911 Ultra-Torque Fastener Assembly Lubricant (20 oz) | Universal
ARP 100-9911 Ultra-Torque Fastener Assembly Lubricant (20 oz) | Universal

ARP

ARP 100-9911 Ultra-Torque Fastener Assembly Lubricant (20 oz) | Universal

SKU: ARP100-9911
$27.26
$52.01
PPE 114020000 PCV Crankcase Breather Repair Fitting Set | 2004.5-2010 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
PPE 114020000 PCV Crankcase Breather Repair Fitting Set | 2004.5-2010 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

PPE

PPE 114020000 PCV Crankcase Breather Repair Fitting Set | 2004.5-2010 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

SKU: PPE114020000
$26.99
Mahle 55026 Right Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Mahle 55026 Right Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Mahle

Mahle 55026 Right Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

SKU: MCI55026
$54.09
$114.43
EFI Live ACV3 Live Blank AC3 AutoCal Device | Universal
EFI Live ACV3 Live Blank AC3 AutoCal Device | Universal
EFI Live ACV3 Live Blank AC3 AutoCal Device | Universal
EFI Live ACV3 Live Blank AC3 AutoCal Device | Universal
EFI Live ACV3 Live Blank AC3 AutoCal Device | Universal
EFI Live ACV3 Live Blank AC3 AutoCal Device | Universal

EFI Live

EFI Live ACV3 Live Blank AC3 AutoCal Device | Universal

SKU: EFIACV3
$595
Mahle 55027 Left Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
Mahle 55027 Left Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Mahle

Mahle 55027 Left Side Cylinder Head Gasket (Grade C 1.05mm) | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

SKU: MCI55027
$54.09
$114.43
Mishimoto MMTS-CHV-01DL Low-Temperature Thermostats | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
Mishimoto MMTS-CHV-01DL Low-Temperature Thermostats | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Mishimoto

Mishimoto MMTS-CHV-01DL Low-Temperature Thermostats | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

SKU: MIMMMTS-CHV-01DL
$101.95
ARP 129-2503 Harmonic Balancer Bolt Kit | 2001-2019 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax V8
IN STOCK
ARP 129-2503 Harmonic Balancer Bolt Kit | 2001-2019 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax V8

ARP

ARP 129-2503 Harmonic Balancer Bolt Kit | 2001-2019 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax V8

SKU: ARP129-2503
$30.42
Edge 85400-200 CTS3 Diesel Evolution Programmer 50 States Legal | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
Edge 85400-200 CTS3 Diesel Evolution Programmer 50 States Legal | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Edge 85400-200 CTS3 Diesel Evolution Programmer 50 States Legal | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Edge 85400-200 CTS3 Diesel Evolution Programmer 50 States Legal | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
Edge 85400-200 CTS3 Diesel Evolution Programmer 50 States Legal | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

Edge Products

Edge 85400-200 CTS3 Diesel Evolution Programmer 50 States Legal | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

SKU: EDG85400-200
$799.95
$899.95
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 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

SKU: WCF100155
$40.74
ARP 230-5401 Main Stud Kit | 2001-2005 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
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

SKU: ARP230-5401
$241.65
$460.91
PPE 119020009 Stainless Steel Heater Hose Connector | 1999-2014 GM Silverado/Sierra 2500HD/3500HD
IN STOCK
PPE 119020009 Stainless Steel Heater Hose Connector | 1999-2014 GM Silverado/Sierra 2500HD/3500HD
PPE 119020009 Stainless Steel Heater Hose Connector | 1999-2014 GM Silverado/Sierra 2500HD/3500HD
PPE 119020009 Stainless Steel Heater Hose Connector | 1999-2014 GM Silverado/Sierra 2500HD/3500HD
PPE 119020009 Stainless Steel Heater Hose Connector | 1999-2014 GM Silverado/Sierra 2500HD/3500HD

PPE

PPE 119020009 Stainless Steel Heater Hose Connector | 1999-2014 GM Silverado/Sierra 2500HD/3500HD

SKU: PPE119020009
$19.79
SoCal Diesel DSP5LLY DSP5 Switch | 2004.5-2005 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax LLY
SoCal Diesel DSP5LLY DSP5 Switch | 2004.5-2005 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax LLY

SoCal Diesel

SoCal Diesel DSP5LLY DSP5 Switch | 2004.5-2005 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax LLY

SKU: SLDDSP5LLY
$55
PPE 119020086 Coolant Drain Tube | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
PPE 119020086 Coolant Drain Tube | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
PPE 119020086 Coolant Drain Tube | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

PPE

PPE 119020086 Coolant Drain Tube | 2001-2016 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

SKU: PPE119020086
$26.99
PPE 119021007 EGR to CAB Coolant Hose | 2004.5-2007 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
PPE 119021007 EGR to CAB Coolant Hose | 2004.5-2007 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

PPE

PPE 119021007 EGR to CAB Coolant Hose | 2004.5-2007 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax

SKU: PPE119021007
$12.14
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

SKU: MAT10479
$79.72
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

SKU: EFIFS3-GM
$1,025
Mahle CS54580 Lower Engine Gasket Kit | 2001-2007 GM Silverado/Sierra 2500HD/3500HD 6.6L Duramax
IN STOCK
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

SKU: MCICS54580
$132.67
$299.37

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DIESEL TRUCK EXPERTS STANDING BY

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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