Diesel Tuner's Blog

Essential 2004.5 and 2005 Duramax Upgrades

LLY is the code used for Duramax motors used in 2004.5 and 2005 HD trucks.  Although they introduced improvements from the 2001-2004 on the LB7 motor, there are a few essential upgrades every owner should consider.  (That is assuming an LLY owner would want more power, lower EGT's and better efficiency.)

Before diving into the pitfalls of an LLY, here are a few of the improvements brought to market when they were released.

• Injectors outside of the heads provided much easier replacement
• Improved injector design much more reliable than its predecessor 
• Variable Vane Turbo technology provides better spool up and wider power band
• Largest frame turbo of any Duramax motor to date

After years of testing this motor and countless upgrades, there are at least 5 essential upgrades every LLY could use.

What is the the best tool a diesel enthusiast could ever ask for; a Mustang 4WD Chassis Dynamometer.  Why is that?  An 4WD Chassis Dyno gives you the ability to see exactly what your truck is capable of.  It also provides tuners the safe and controlled enviroment required to test calibrations and dial in your truck to best running condition.  Which in turn, gives you a truck that not only makes big power, drives as smooth as possible and gives you insight to when and how your truck performs at it's best.  

• Find your PEAK Horse Power and Torque
• Get the smoothest running truck possible
• Gain insight into how and when your truck performs it's best

Many people have estimated horse power and torque numbers based on what someone else has told them.  A Chassis Dyno gives you the ability to know exactly how much power you have at the wheels.  No guessing or estimating involved since a dyno is a measurement tool at it's core.  

Beyond peak power, there is drive-ability to consider when you have a heavily modified truck.  Any tuner can make the peak power number, the difference between them is how the truck drives on the street.  Smoke output, shift points, throttle response and so much else can be dialed in when you are strapped to a dyno for testing.    

Diesel truck owners often want more RPM.  The logic here is that RPM equals power.  However, a chasis dyno gives you a clear picture of where and when your truck makes peak power.  When it comes to competing with your truck, this is crucial!  Diesel guys know all too well how close sled pulling or drag racing can be, so every possible edge really matters.  

Stock Duramax Turbo Upgrades!

Duramax owners are generally proud of how their stock turbos perform.  They spool quickly, run hard and are capable of over 500 RWHP (once you tune it and make a few supporting modifications to handle the power).  However, after driving your truck around 520 RWHP for a while, the addiction will creep in and you may find yourself shopping for more power.  We all do it!  For some, it may not even be about more power, it may be about EGT control under load, or it may just be the factory turbo had an issue and needs to be replaced.  If you are anything like me, you will not want to replace it with the factory components if there is an upgraded, after market, charger available. 

• The LLY Duramax  is a great truck from the factory for there are 3 modifications every owner should make! The LLY was manufactured 2004.5 and 2005. There are a few 2006 models that are labeled as an LLY, however they have all of the LBZ upgrades from the factory, so for performance applications consider those an LBZ. An LLY was the first Duramax with the injectors outside of the heads, a variable vane turbo and a 50 state EGR.