Diesel Tuner's Blog

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.

The 5 & 6-speed Allison 1000 transmission, paired with 2001-2019 6.6L Duramax, is renowned for its durability and performance, especially in heavy-duty applications. Whether you’re towing, hauling, or simply looking to enhance your driving experience, upgrading your Allison 1000 can make a significant difference. Here are the top five upgrades to consider for maximizing the performance and longevity of your Allison 1000 transmission.

The ten-speed Allison 1000 is substantially better than previous Allison models we have seen come in Duramax trucks. Known for its superior towing performance, excellent fuel economy, and outstanding reliability. It utilizes some of the best technology GM has ever produced. Its reputation for excellence was earned largely because of the advanced electronic control systems provided by the TCM (Transmission Control Module).

As technology gets better, we see transmissions in trucks with more and more gears. Recently the Allison 6-speed was replaced with the 10-speed version. For older trucks, this can set them behind the competitors, both in terms of performance and fuel efficiency. A 6-speed conversion kit can take LB7 and LLY trucks to a whole new level of performance and drivability. 

If you are already in need of a valve body replacement due to slipping gears because of a weak or bad solenoid this kit is exactly what you'll want to swap in its place. The kit comes with an upgraded valve body combined with a 6-speed TCM. This upgraded TCM comes with updated shift schedules customized to your truck for the new gearing . Calibrated Power has been able to design one of the smoothest shifting 6-speed conversion kits there is. This kit will have your 15-year-old truck shifting like a 2018 model. It's also relatively simple to install and can easily be installed by someone who knows what they're doing in the shop or at home. Another option is to have Calibrated Power install it themselves in one of their upgraded transmissions (DT550, DT750, or DT1000), which is what you'll want if you're trying to make big power. 

If you're looking for any of these qualities out of your transmission then a 6-speed conversion is for you:

• Better MPG's
• Quieter Exhaust Drone On The Highway
• Smoother Shifting Transmission 
• Engine and Transmission Longevity
• Narrower Cruise Range to Meet Emissions Requirements

The Six Speed Conversion Kit from duramaxtuner.com has been unleashed and it’s a proven winner.  The fifth gear days of yore have passed the world by and the 2001-2005 LB7 and LLY owners are loving how much more the extra gear brings them.  Large amounts R&D and testing has given 5 speeds a better shift schedule and the highest quality 5-6 and 6-5 shifts. The upgraded valve body with have your aging truck shifting like a new model.

6 Speed Conversion Kit for the LB7 & LLY 5 Speed Allison:

Your 2001-2005 Silverado/Sierra HD diesel is powered by either the LB7 (2001-2004) or LLY (2004.5-2005) Duramax.  That Duramax is tied to one of the most popular automatic transmissions, the Allison 1000.

While the Allison 1000 was a big step forward, it still needed improvement.  The LB7/LLY models came with 4 gears and Overdrive, or "5 speed".   In 2006 General Motors (GM) released the 6 Speed transmission for the new at the time LBZ model and other HD trucks. 

Without getting too technical about how automatic transmissions work, they did not actually add a physical gear.  The Allison works through a series of clutch packs being applied with hydraulic pressure to create different gear ratios.  What GM actually did was design a brand new valve body and improved tuning to achieve the 6 speed Allison 1000.

DuramaxTuner.com now has a 6 Speed Conversion Kit which includes a new valve body and custom tuned TCM that allows your truck to achieve 6th gear.  

Who Will The 6 Speed Conversion Kit Help?

• Owners wanting a quieter ride
• Drivers looking for a smoother shifting transmission
• Highway commuters