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.
Key Features of the DT Series STR Transmission
Upgraded + Added Clutches: Power and Reliability in Every Shift
One of the standout features of the DT Series STR transmission is the clutch upgrades it receives. In later model Duramax's like the LML and L5P additional clutches were added to the C1 and C4 clutch packs to increase the power handling capabilities for the increased HP of modern. However, simply upgrading the C1 and C4 clutches isn't enough to satisfy most consumers expectations for power handling capabilities with the added power from tuning or long term reliability under heavy towing conditions. Thats why the STR gets additional clutches added to every clutch pack.
- C1 - C4 Raybestos GPZ/Borg Warner Clutches: These clutches provide improved torque capacity and high heat resistance, meaning your transmission can handle more power without overheating or slipping under load.
- C5 Raybestos Clutches: These are added for improved durability and smoother engagement, ensuring that you won’t experience rough shifts, even when under load.
- Better Durability than Stock: These upgraded clutches maximize the reliability of your transmission, ensuring that it stands up to the test of time.
- Made in the USA: Built to the highest standards, these clutches offer long-term performance and peace of mind.
Updated Electronics: Smooth and Reliable Shifting
The electronics in your transmission play a crucial role in overall performance, and the DT Series STR takes them up a notch for improved reliability for years to come:
- New Neutral Safety Switch & Speed Sensors: All OEM electronics and sensors ensure smooth and consistent operation.
- Solenoids Testing Performed In-House: Each solenoid undergoes rigorous testing for enhanced reliability, so you know your transmission will operate trouble-free for years.
- Long-Term Reliable Performance: Updated electronics contribute to the transmission’s overall durability, allowing for trouble-free, high-performance operation under heavy-duty conditions.
Upgraded C3/C4 Return Springs: Better Shifts
The C3 and C4 return springs in an Allison 1000 transmission play a critical role in the proper operation and longevity of the transmission’s clutch packs. These springs are responsible for ensuring that the C3 and C4 clutch packs fully disengage when they are not in use, preventing unnecessary drag, excessive heat, and premature wear. Here's how the STR improves their function for added reliability and performance:
- More dependable shifting: No more worrying about inconsistent engagement or harsh shifts.
- Improved Shift Quality: The springs ensure smoother, quicker shifts under varying load conditions, enhancing overall driving comfort.
LML Dual Disc Torque Converter: Built for Power and Towing
The torque converter in the Allison 1000 transfers power from the engine to the transmission, allowing smooth acceleration and preventing stalls. Its lockup clutch enhances efficiency by creating a direct mechanical connection at higher speeds. If you’re hauling a trailer or towing a heavy load, the dual-disc torque converter in the DT Series STR transmission is a game-changer for power handling and transmission.
- Superior Strength: This torque converter is significantly stronger than the stock LB7, LLY, LBZ or LMM torque converter, providing better power handling strength and power transmission.
- 1800-1900 RPM Stall Speed: This torque converter also provides the ideal stall speed for towing and daily driving, offering a smooth, consistent lock-up for better fuel efficiency and smooth yet snappy performance.
- Increased Reliability for More Power: Designed to handle increased power output, this torque converter ensures that your truck maintains reliability and performance even under heavy stress or added power.
Transmission Case: Ready for Future Upgrades
The STR transmission case is pre-drilled to accept the C3 Oiler upgrade, which, even if not selected now, can easily be added in the future. This means you won’t have to swap out the entire transmission to make upgrades later on.
TCM Tuning Included: Maximizing Performance and Durability
One of the most important features of the DT Series STR transmission is that TCM tuning is included with your purchase. This custom tuning electronically enhances your transmission’s performance, giving you significant benefits, including:
- Increased Line Pressure and Clutch Holding Force: These adjustments ensure your transmission can handle the extra power, preventing slipping under load and maximizing its performance capabilities.
- Better Towing Performance: With smoother shifts and reduced heat buildup, your transmission will perform better when towing heavy loads or driving on long trips.
- Optimized Shift Points: TCM tuning allows you to select shift points that maximize either performance or efficiency, depending on your driving needs.
- Reduced Wear and Tear: Proper line pressure and torque management help reduce the stress on your transmission, ensuring it lasts longer.
- Quicker and More Responsive Shifts: You’ll enjoy a much more engaging driving experience with faster, smoother shifts that put you in control.
Not only does the TCM tuning offer performance improvements, but it also pairs perfectly with ECM tuning, allowing for a fully optimized performance package. Whether you’re looking to increase horsepower, improve towing capability, or simply enhance your truck’s drivability, the DT Series STR transmission combined with tuning is the way to go.
Optional Upgrades to Take Your Transmission to the Next Level
The DT Series STR transmission also offers some optional upgrades to further enhance its performance and longevity:
- C-3 Oiler: This upgrade provides additional lubrication to the clutches, improving overall longevity and reliability. It's an ideal option if you're pushing your transmission to its limits.
- Deep Pan: A deep pan increases fluid capacity, helping to keep your transmission fluid cooler and cleaner, which extends the life of your transmission.
- Upgraded 6-Speed Valve Body (For 2001-2004.5 LB7 and LLY Duramax's): This upgrade converts your 5-speed to a 6-speed, offering quicker, crisper shifts and a brand new valve body for maximum responsiveness.
Built for Power: Towing, Load Handling, and Durability
The DT Series STR Transmission is designed to handle over 500HP and 1000 ft-lbs of torque, making it the perfect choice for those running custom tuning or pushing their truck’s performance to the limit. Whether you're towing a boat up a steep grade or driving through challenging off-road terrain, this transmission is engineered to handle the demands of gross vehicle weight (GVW) loads without the fear of slipping or premature wear.
With the added clutches and torque converter, you can rest assured that the STR transmission will keep your power under control, providing smooth, positive shifts no matter how heavy the load. Unlike stock transmissions that can often struggle under stress, the STR ensures reliable performance, even in extreme conditions.
For those who daily drive their trucks, tow frequently, or just want a more reliable Allison 1000 transmission, the STR transmission provides smooth, consistent shifting with an easy converter lock-up, ensuring that your truck feels like it’s built for the long haul.
A Warranty Thats Says "We Stand Behind This Product"
DuramaxTuner stands behind their entire line of DT Series Transmission's including the STR with a 3-year standard or 5-year extended warranty (+$500). This warranty ensures that your investment is protected, giving you peace of mind that your transmission will perform as expected, year after year. Whether you're looking to increase towing capacity, enhance daily drivability, or simply improve reliability, the DT Series STR Transmission comes backed by a team that believes in its performance and quality.
Conclusion: Why Choose the DT Series STR Transmission?
If you’re looking to replace or rebuild your stock transmission, the DT Series STR Transmission offers best-in-class upgrades at an affordable price. With its upgraded clutches, stronger electronics, dual disc torque converter, and TCM tuning, the STR is built to handle powerful loads, high torque, and heavy-duty demands, all while maintaining smooth shifts and reliable performance.
Whether you’re towing, daily driving, or pushing your truck to the limit, the DT Series STR Transmission will maximize your truck’s performance potential for years to come. And with a solid warranty backing it, DuramaxTuner ensures that you’re not just getting a product, you’re getting peace of mind.
Make the smart choice for your truck and choose the DT Series STR Transmission today. Your Duramax deserves it.
