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.

• 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.