Diesel Tuner's Blog

What Can TCM Tuning Do For Towing with my Duramax?

Posted by Paul Wilson on Jul 21, 2017 8:50:00 AM

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.

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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. 

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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. 

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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.  

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TCM Tuning is not required on these trucks, but for the cost very few people pass it up.  It makes a night and day difference in how the truck feels.  No, it wont gain you more mileage.  No, it wont add horsepower.  It will put a smile on your face every time it shifts the way you want it to.  


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Click the button below and fill out the form on the corresponding page.  

One of our specialist will contact you as soon as possible to help you out! 

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Topics: TCM, towing, towing performance, LML TCM Tuning, TCM Tuning, LMM TCM Tuning, LBZ TCM Tuning, LLY TCM Tuning, LB7 TCM Tuning