Your Duramax-powered Chevy or GMC was built to tackle tough jobs with ease and deliver years of dependable performance. But when you push these trucks to their limits on a daily basis, reliability can quickly become a concern. While the engine is often up to the task, the factory transmission is usually the weak link—struggling under the added stress until clutches start slipping and failures begin. In many cases, a transmission rebuild or replacement is needed long before the engine shows any signs of trouble. And if you frequently push your truck to the max, even a rebuilt transmission may not hold up for long.

That’s exactly what inspired the development of the all-new DT Series STR Transmission. Designed for stock and mild-tuned trucks, the STR is built with key upgrades that stretch your budget further by maximizing durability and reliability. Whether you're replacing a worn-out stock unit or upgrading to gain a little more capability, the STR delivers the strength and performance you need to handle heavy towing and increased power from tuning—without the constant worry of another rebuild.

If you’re a Duramax diesel enthusiast or truck owner, you’re likely familiar with the Allison 1000 transmission. Revered for its durability, smooth shifting, and ability to handle the power of diesel engines like the GM Duramax, it’s a popular choice in heavy-duty trucks. However, even the best transmissions aren’t immune to problems. In this detailed guide, we’ll combine insights on diagnosing common issues, troubleshooting tips, and upgrading your Allison transmission to ensure your truck keeps running strong under any condition.

The Allison 1000 transmission has long been a cornerstone of GM’s HD truck lineup, particularly in conjunction with the Duramax engines. Over the years, this transmission has undergone continuous refinements to meet the evolving demands of power, performance, and emissions standards. In this post, we'll break down how the Allison 1000 transmission has evolved across six generations of the Duramax engine family: LB7, LLY, LBZ, LMM, LML, and L5P, highlighting key changes and comparing performance across each year range.

Diesel engines have many nuances when compared to their gas counterparts, fuel injectors being one of them. Unlike fuel injectors used on direct injection gasoline engines, diesel injectors often have a higher failure rate and shorter lifespan due to their more extreme operating conditions. When these injectors fail, it can lead to a cascade of performance issues, increased emissions issues, and even engine damage.

Over the years, GM has changed a lot regarding the turbos they use on Duramax engines. Not only have they changed manufacturers a handful of times but each RPO has its own unique measurements for key components. This can make it a headache when trying to track down exactly what the measurements of your stock turbo are. Luckily we've compiled this list of stock Duramax turbo specifications along with other helpful information so you can get a good idea of what you're already working with before you dive into the sea of turbo upgrades these trucks have to choose from. However, while some turbos may have the same peak power output, the size and shape of specific components can affect things such as exhaust gas temperature, drive pressure, and turbo efficiency range.  

What's an RPO? Crucial Duramax Information!

This article will help you understand what an RPO is, how to find yours and when it will be needed.  An RPO or Regular Production Option is a GM-specific code, made up of 3 characters, that helps the manufacturer specify what configuration of options has been or needs to be applied to a vehicle. This can include anything from paint color to powertrain options. For Chevy/GMC Duramax trucks each type of engine can be signified by a different RPO code.

We have lowered our MAP pricing on the Stealth 64 Turbo:

Calibrated Power, home of DuramaxTuner.com, has ramped up in-house production of the Stealth Turbo line.  This added capacity and volume of turbo production has provided an opportunity to lower MAP pricing on all Duramax models and allowed the Cummins 5.9L Stealth 64 to be a low price and top quality leader in it's category. 

Our Stealth 64 Turbo's are:

• Made in the USA!
• Upgraded, Drop-In Replacement!
• Quick Spooling with Big POWER!

Duramax VVT Upgrades:

The 2004.5-2005 LLY was the first model Duramax to be equipped with a Variable Vane Turbo (VVT).  VVT  technology provides quicker spool-up, better EGT control, and better overall boost control.  This is also commonly referred to as a VGT or Variable Geometry Turbo. 

To understand the basics of a VVT or VGT technology take a look at this VIDEO on YouTube.

The stock Duramax VVT turbo from 2004.5 until 2010 is similar.  Slight changes to each model (LLY, LBZ and LMM) were made in compressor size, aspect ratio, blade profile and other features.  Despite these changes, you will find the same peak power potential of approximately 530 RWHP.  As a Duramax performance enthusiast this is probably just not enough power to keep your interest for long. 

There are many upgrade options on the market.  Deciding which one is the best for you can be tough.  An endless amount of forum threads and user stories makes it challenging to decipher fact from opinion.  

Stealth 64 Turbo Product Links:

• Stealth 64 LB7
• Stealth 64 VVT
• Stealth 64 LML