If you own a 2006–2015 Chevy or GMC Duramax 2500 or 3500 with the Allison 1000 transmission, you likely know that the Transmission Control Modules (TCMs) are a notorious weak point. These modules have caused major headaches for truck owners in recent years, often leaving vehicles in limp mode or completely stranded.

In this article, we’ll cover what the TCM does, the most common signs of failure, and talk about the pros and cons of new vs. remanufactured modules.

What is an Allison TCM and what does it do?

The TCM is the brain of the Allison 1000 transmission, using data from various sensors to control gear shifting and ensure efficient operation. It’s essentially the middleman for communication between the transmission and the rest of the vehicle. Without a properly functioning TCM, the vehicle won’t be able to drive.

The T14, T14a, A40, and A50 TCMs were used specifically in 2006–2015 Duramax trucks with the 6.6L engine. Unfortunately, these modules are prone to internal failure due to poor manufacturing techniques and gradual wear over time.

How Do I Know if my Allison TCM is Bad?

When the TCM begins to fail, several warning signs may appear. The most common issues include:

• Communication Loss: Often the first symptom, the vehicle loses connection with the TCM.
• Diagnostic Trouble Codes (DTCs): U0101, U0100, or P0700.
• Failure to Shift Gears: The truck may refuse to shift or get stuck in one gear.
• Harsh or Erratic Shifting: Shifts become unpredictable and rough.
• Limp Mode: The truck becomes stuck in 3rd gear, limiting drivability.

You may experience one or more of these symptoms at the same time. Unfortunately, TCMs can fail quite suddenly, leaving you stranded without warning.

Why Do Allison TCMs Fail?

Allison TCMs fail for several reasons. The original manufacturing methods used to produce the modules are unreliable. Because the module is exposed to a large amount of heat and vibration for an extended amount of time, internal connections are prone to breaking. In addition, components on the circuit board can fail completely, leading to any number of failure symptoms.

Why Rebuilding is the Best Option

There are a few options to choose from when looking for replacement TCMs. You could try to find a brand-new module or get a remanufactured TCM. Knowing why the TCM failed in the first place is crucial when making this decision. New modules use the same methods of manufacture that caused your original to fail. They’re also more expensive, with longer shipping times, and poor customer service backing.

At Circuit Board Medics, we remanufacture Allison TCMs to function better than new. We don’t just fix a single failure. We fully remanufacture these modules to address all known failure points to prevent problems down the road. Our rebuild targets the root cause of issues and fixes the shortcomings of the original manufacturing process.

Benefits of our Allison TCMs:

• No Core Charge Upfront: When your new module arrives, just return your old one in the same box.
• No Programming Required: Your module will be completely plug-n-play.
• 2-Year Warranty: Every rebuilt TCM is backed by our industry-leading warranty.
• Precision Rebuild Process: Using advanced PCB rework equipment, including wire bonding and BGA rework, we ensure next-level reliability.
• World Class Customer Support: Our technical experts are ready to assist either before or after installation.

Do Allison TCMs need to be programmed?

Yes, Allison TCMs need to be programmed to work properly with your vehicle. There are many part numbers of the TCM, so it’s crucial that you get the correct part and then also have it programmed to your VIN. We handle all of this for you based on your order, so all you need to do is enter your VIN or engine serial number and we’ll ensure your TCM is programmed and ready to go. In addition, we offer optional custom tunes that will enhance your truck’s performance with improved shift points.

How to Fix an Allison TCM

Getting your truck back on the road is simple:

1. Check out our exchange service
2. Provide your VIN and place your order.
3. Install the remanufactured TCM when it arrives.
4. Return your old module in the provided box.

If you’d rather order by phone or have questions about the process, call us at (800) 547-2049 and speak with one of our experts. We look forward to serving you!