How does Allison 1000 TCM Tuning help with towing?
TCM Tuning is the modification to the programming calibration of a Transmission Control Module (TCM). Ever since 2001 when the Duramax was first offered in the 2500 and 3500 GMC and Chevy HD truck it has been paired with the Allison 1000 transmission.
These trucks are designed for towing and if you use it that way, you can probably think of a few ways you would like your transmission to act differently. That is where TCM Tuning may be able to help.
Common Complaints About Stock Transmission Tuning:
- "When I try to pass and I am in 6th gear, it is very reluctant to downshift."
- "While merging on the express way it seemed to take a long time to get from one gear to the next. It's even worse with a trailer on."
- "Even with tow haul mode on the truck doesn't seem to shift well since I put these larger tires on."
TCM Tuning can dramatically help with drive-ability but it's not a band-aid for a weak or damaged transmission:
This list will help you guide through the most common questions about TCM Tuning. If you have more questions about your specific truck or application just click the button below to request more information and fill out the contact form. We will follow up with you as soon as possible.
1. LB7 & LLY (2001 - 2005)
The first 2 generations of the Duramax equipped HD trucks came with a 5 speed Allison 1000. This is the weakest version of the Allison. Commonly people find the 4 to 5 up-shift and 5 to 4 downshift an issue. Under heavy throttle, especially with aggressive tuning or while under a high engine load, the transmissions tends to slip and cause a "Limp Mode". This means you are locked in 3rd gear and will at the very least, need to shut the truck off and turn it back on to clear the safety mode.
Transmission tuning will NOT solve this problem. The issue is with the physical integrity of the hard parts in the transmission, not with the calibration. For the 5 speed Allison TCM tuning can raise shift points. This will dramatically help you if you're running large tires. The rule of thumb at DuramaxTuner.com is if you have larger than 35" tires, you NEED TCM Tuning. Running larger tires effectively changes the gearing on your truck, which is why changing the shift points will help balance this out.
Also, raising shift points will help if you have larger than a 64mm turbo. Larger single turbo's run in a different efficiency range. Meaning the stock TCM tune will not keep the truck in the best running RPM. If you have something like the Stealth 64, there is no need to worry about TCM tuning. Your stock calibration keeps those turbo's happy.
2. LBZ & LMM (2006 - 2010)
In 2006 the 6 speed Allison 1000 was introduced to the HD pickup. Stronger, more reliable, smoother shifting, and a stronger torque converter, it really was ahead of it's time. If you have towed with either the 5 or 6 speed than you certainly agree the 6 speed is preferable. The extra gear means even while in tow haul mode you gain the ability to reduce RPM even further than before. With an improved clutch pack design and more electronic control GM trucks were able to boast even smoother towing than before.
Maybe surprisingly, the 6 speed Allison has a lot to gain through the proper Custom TCM Tuning. Despite all their improvements, they are reluctant to downshift, slow to get from one gear to the next and lacking in lock-up strategy. With more extensive electronic control than it's predecessor this can all be addressed through TCM Tuning.
The reluctance to downshift is most noticed in 6th gear. The stock calibration can leave you with your foot almost on the floor before it decides to drop a gear and go. Frustrating is the nicest way to describe this when you are trying to pass or get around someone. The same goes for how long it takes to get from one gear to the next while under acceleration. Many call it "De-Fuel" or say that it falls on it's face between gears. In reality this can be fixed by matching your ECM and TCM tuning.
The last feature that TCM Tuning can assist with is the torque converter lock-up strategy. Lock-up is something that anyone with a trailer on knows is important. You have to put the power on the ground and that's exactly what locking the torque converter does. This is why it is so imperative to match the lock-up strategy to the design of your ECM tuning.
3. LML (2011 - 2016)
The LML features the strongest stock transmission to be offered by General Motors (GM) for the HD line. In stock form it has been pushed to 600HP and held up quite well. Again, when released it pushed further into electronic control. Increasing the commanded line pressure helps increase clutch holding capacity. Torque converter lock-up is even further refined in it's parameters and the stock torque converter is a jump and leap above what we have dealt with in the past.
4. L5P/L5D 2017 - 2019 (6-Speed)
The 6-speed Allison 1000 found in the L5P/L5D (2017-2019) Duramax trucks introduced a series of significant improvements over its predecessors, including enhanced durability and smoother shifts. However, these trucks can still benefit from custom TCM tuning, especially if you’ve added performance upgrades such as ECM tuning, a larger turbo or aftermarket intake. The stock shift strategy on these models is programmed quite conservatively, meaning your truck can feel slow to respond under hard acceleration or when towing heavy loads.
One of the most noticeable issues with the 2017-2019 L5P/L5D trucks is the delay in downshifting when you need it most, such as when merging onto highways or towing up a grade. Custom TCM tuning can resolve this issue by adjusting shift points, improving responsiveness, and ensuring the transmission shifts at the optimal RPM. Additionally, tuning the torque converter lock-up strategy can further enhance power delivery, especially under load, ensuring that the full power of your engine is transferred to the wheels efficiently.
If you're running larger than stock tires or have made upgrades to increase horsepower, custom tuning is essential to get the most out of your truck and prevent unnecessary transmission strain.
5. L5P/L5D 2020 - 2023 (10-Speed)
With the L5P/L5D models from 2020 to 2023, GM has continued to refine the Duramax engine and Allison transmission, pushing the envelope in terms of power, torque, and overall towing capability. These trucks come with an all new 10-speed Allison transmission, which offers more gears for smoother shifts and better fuel efficiency. However, despite the advancements in towing performance and fuel economy, they still exhibit many of the same common issues seen in older models, along with a few new quirks that can hinder your comfort and feeling of power while driving.
One of the biggest complaints to plague specifically the 10-Speed Allisons is the massive delay time in between shifts. This can at best make the truck feel like its not even shifting gears at all and at worst create a noticeable lack of power in-between gears. You can see this this massive dip in power illustrated by the green line in the dyno graph above. The red line on the other hand displays the significant reduction in de-fuel times and significant increase in overall power making it to your wheels over all 10 gears that custom TCM tuning can provide 10-Speed Trucks.
Custom TCM tuning is even more important with these newer models due to the increased complexity of the 10-speed transmission. The additional gears can sometimes lead to hesitation or "lag" between shifts, particularly under heavy acceleration or towing. By tuning the TCM, you can ensure that the transmission shifts more aggressively and efficiently, enhancing towing performance and driving feel. Additionally, optimizing the torque converter lock-up and shift points can provide a smoother, more responsive driving experience, especially when working your truck hard.
Whether you're pushing high horsepower with a built engine or just want a more responsive daily driver, custom TCM tuning will ensure your L5P/L5D operates at its full potential.
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