Allison 10L1000 Transmission • Problems and Solutions (2023)

Introduction to the Allison 10L1000:

To get straight to the point, the Allison 10-speed 10L1000 was introduced for the 2020 model year in General Motors Silverado and Sierra heavy-duty trucks and is currently in service. This gearbox is by far the most robust, well-engineered and dynamic gearbox that could be paired behind the DuraMax series trucks to date.

It is the successor to the 6-speed Allison 1000 transmission, whose tenure began in 2001 with the LB7 DuraMax and ended in 2019 under the L5P years. You can learn more about the 2001-2019 Allison 1000 transmission by reading our

Allison 10L1000 Transmission • Problems and Solutions (1)

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In fact, it has the highest relative torque capacity of any transmission yet released in this class, easily outperforming competitors like the AS69RC or 6R140. One thing to note about the Allison 10L1000 is that this transmission is a fraternal twin of the Ford TorqShift 10 Speed ​​10R140. In fact, the internal components of this transmission are largely interchangeable with those of the Ford, the parent engineer of this product.

While this is generally a "good" transmission, there are a number of easy-to-solve problems that simply require data analysis and technical understanding. In fact, we've compiled all of this data into our version of the 10L1000, shown below.

With that in mind, without further ado, we'll address the most productive issues, fixes, and upgrades available for the new Allison 10-speed 10L1000 transmissions.

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The Allison 10L1000 Product Resource:

- 10L1000 gearbox
- 10L1000 torque converter
- 10L1000 conversion kits
- 10L1000 valve body
- 10L1000 for you

Popular sources for transmission information:-Top 5 benefits of an upgraded or built gearbox
-Torque multiplication factor calculation, why is it so important?
-Top 5 Ways to Extend the Life of a Factory Transmission

In this Drivetrain 101 we will address the following:

(Video) New Allison and Ford 10 Speed Diesel Transmissions

- The most common faults we see with the Allison 10L1000 transmission

- Its capabilities (or lack thereof) in terms of TCM tuning and shift/lockup protocol modification

- The strengths (believe it or not, there are a few!) of this transmission

- Footnotes for ChevroletANDGMC owners

And a lot more!

Problem #1 – The torque converter lock-up mechanism

If this transmission has an Achilles heel, it's the woefully inferior OEM torque converter. There's a lot of good AND a lot of bad, so we've broken this down into several sections. The problem here, ironically, isn't the design, but a fun mirror version of Ford's 6R140 torque converter lockup mechanism. Ford's 6R140 lockup mechanism was excellent in that it faced the stator and not the flexplate.

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Extremely heavy duty transmissions such as the 10L1000, 6R140 and AS69RC feature converters with reversed or “backward” lock-up mechanisms for reasons of overall reliability, thermal management and oil coupling. It's a healthy improvement in durability when this advance in technology takes place, but that doesn't make the device perfect.

The reality is that the torque capacity of this lockup mechanism, while difficult to test due to variables, seems to die at virtually any power level above factory OR when the tire size is greatly increased without a proper retrofit. Statistically speaking, trucks over 500 hp or that want to pull extremely heavy will not survive long. Luckily we offer 2 different Billet Multi-Friction Torque Converters for those who fear this problem.

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Problem #2 - The Stator

(Video) Diesel Insights: Allison 1000 Transmission

The stator, the part within the torque converter that controls stall speed, is incredibly fragile and contributes to thermal management complications. This is an inferiority that has plagued Ford, and even more so GM/Allison, in the diesel community for years. Despite the inferiority of Dodge converters, they also have the strongest stators that we have tested in factory form. Anyone who wants to upgrade this torque converter must therefore make modifications to the stator.

The solution here is multifaceted, the first thing to do is find a stronger material to make the stator out of. As a result, CNC machined and often billet (depending on the application) stators are used to eliminate the usual rotation, cracking, or yawing that geometrically affects this item's ability to perform reliably.

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To put it simply, any 10L1000 or 10R140 torque converter with an unmodified OEM stator is more likely to fail. For this reason we do not use a stock stator in any of our 10L1000 torque converters. We prefer to precision machine the converter's stator, which gives us omniscient control over stall speed.

Problem #3 - Functional problems caused by additional power supply

This brings us to a subsequent point, the elements of friction. As mentioned, this is an exceptional design, but the diesel community is no stranger to tuning platforms like EFI Live or EZ Lynk, used to improve economy, performance and functionality. As a result, this converter is often required to withstand more power than it was ever designed for, forcing the aftermarket to step in.

For this reason, all customers who even want to do a tuning on this truck should understand that the clutch and steel stacks in the gearbox are generally only sufficient for the torque that the truck produces from the factory, and practically no more. This requires the implementation of billet pistons, billet reaction plates, and redesigned clutches and steels that are appropriate in dimension and quality to meet consumer needs.

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On the subject of friction elements and torque converters and how they are challenged by additional power, the 10L1000 and 10R140 have the unique ability to achieve lock-up as early as 1st gear to aid in thermal regulation. The fluid coupling generates approximately 70% of the heat generated by this transmission, depending on air pressure, stall speed, power train and other thermostatic factors. For this reason, it is imperative that a torque converter is designed with durability, thermal management and power capacity as priorities.

Modifications like those described above allow us to craft a unique torque converter that achieves these 3 goals in beautiful trichotomy. The diagram below can be used to identify the appearance of the various converter parts as well as the physical location of other clutch packs within this transmission.

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Problem #4 - The "E" clutch hub

This is a difficult question. Deep within the transmission is the “E” clutch, which is active in first, third, fifth, sixth, seventh, eighth and ninth gears, making it by logical standards the most used and abused clutch in the transmission. This clutch is colored red closer to the rear of the gearbox in the diagram above.

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As with all late '80s Ford TorqShift designs, the aluminum castings from which such components are made are susceptible to aggressive wear and irreparable damage. In fact, most 10L1000s and 10R140s that we've seen with extra power show significant wear on that particular component.

As a result, one would find it illogical not to make this part out of steel instead of weaker but lighter aluminum. The factory is making more and more parts out of aluminum to minimize negative inertia, a physical force that counteracts the combustible propulsion generated by the engine's functional cycles. The problem is that most things made out of aluminum can only survive their own warranty period with storage current.

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However, it is easy to see that making this component out of steel is a safe decision. It should also be noted that the clutch volume of this component is too small. This unit comes with 5 clutches from the factory, but 6-7 will be needed for any truck with extra power or intent on high mileage operation.

A specially machined steel “E” clutch hub allows these two issues to be addressed simultaneously by converting to a stronger material and improving the design to increase torque capacity and heat dissipation from added friction and steels.

The result of implementing both in the same transmission is smooth, crisp and predictable shifts you can depend on for years to come, no matter what's behind you or ahead. That makes this a critical part of a properly built 10L1000 transmission.

Problem #5 – The OEM oil pan

This is a brief inferiority, but it's worth discussing. These pans, much like the rest of the gear industry, are made from stamped metal that is heated and then naturally cooled to hold its shape. This is a problem for many reasons:

  • It does not allow for a true mating surface where the pan mates with the housing as there is no precise flattened surface on the pan side.
  • The pan is incredibly thin and certainly cannot withstand rough use. Off-roaders should beware of factory pans.
  • The sump is nowhere near large enough, this transmission requires more fluid to operate at peak power and cool temperatures, the factory sump prevents this by negating a potential safe increase in oil. This forces the transmission to run hotter than it should, drastically affecting the life of the friction elements inside the transmission and torque converter.
  • The pan does not have enough surface area to properly dissipate heat, heat goes where there is a lack of heat. Because heat is a form of energy. Increases in surface area improve a metal's ability to dissipate heat to the environment.

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Problem #6 - The high pressure oil pump

The oil pump on the 10L1000 transmission is somewhat similar to TorqShifts later models in the sense that the impeller hub (pictured below) is splined to fit directly into the pump. The torque converter impeller hub is the component on the back of the converter that sits inside the pump to rotate the central pump gear that creates pressure.This is designed to better distribute the torque load across the pump and impeller hub to minimize failures.

This is a plus, but an inferior torque converter and combination of clutch assemblies forces the pump to regularly eat up clutch material and steel particles. The end result is that this pump is destined for a reduced lifespan in a factory transmission due to indirect factors affecting its health. Stronger clutch packs, designed for the application rather than struggling to meet their obligations, contribute to a much more durable high-pressure oil pump in the Allison 10L1000.

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Problem #7 - The valve body

Ford has been known in the past for developing such products with ZF-based valve bodies. This time, however, it appears to be a more proprietary design. The valve body in this transmission suffers from the same wear complications as the high pressure oil pump. However, there is the added complication of the relationship between the valve body and the electronics of the transmission.

Once a valve body starts to wear out in this transmission, there is absolutely no regenerative solution. Galvanic wear takes a tremendous toll on this valve body and that process begins the day it leaves the dealer. The solution here, as with the pump, is to ensure that the valve body is given the right conditions for success from day one; a properly built gearbox that doesn't hurl masses of particles of matter through those delicate hydraulic components.

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Problem #8 – The electronics

The most complicated transmission ever built into the DuraMax line, this transmission features an input speed sensor, two intermediate speed sensors, an output speed sensor and an internal mode switch all trying to work together. This leaves a lot of room for complications, especially in a device as computationally intensive as the 10L1000.

This isn't a productive problem that warrants reinventing the wheel, but it's worth understanding the electronically intensive unit that this is. If we have any critical advice for the 10L1000's electronics, it's the same advice we give for any gearbox:

Only use OEM electronics when overhauling the gearbox!

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We are no strangers to cheaper, imported aftermarket electronics; In fact, we tested them in several different environments to gather data on their reliability. While we've had very inconclusive results, as effective investigation would take years, the general correlation is that non-OEM electronics have a disproportionate chance of being bad right out of the box and failing within the first 12 months of use . However, we only use OEM electronics in all of the transmission overhauls we perform.


The 10L1000 is a long-awaited and much-needed advancement in Allison's complex and innovative line of transmissions. As the latest entry in this saga, expectations are high and unfortunately it cannot survive everyone. For this reason we have researched and collected this transmission to the best of our knowledge and belief in order to produce the highest quality product. To find moreCheck out our Allison 10L1000 catalogue, see here:

>>>Allison 10L10000 transmissions, conversion kits and parts

(Video) How to Rebuild a Allison 1000 Transmission | Duramax

For more information on the 10L1000 gearbox or gearboxes we support, contact one of our experts!

Allison 10L1000 Transmission • Problems and Solutions (13)


Are there problems with the 10-speed GM transmission? ›

What's Wrong With GM's 10-Speed Transmission? Class action attorneys are investigating GM models such as Chevy Tahoe, Chevy Silverado and GMC Sierra vehicles because of reports of transmission problems such as harsh shifting, shuddering, hesitation, gear shifting problems and loss of power.

What would cause an Allison Transmission to not shift in gear? ›

This may be caused by low fluid level, valve body problems, a faulty pressure switch manifold, or problems with the wiring or connections; repair as needed.

How reliable is the Allison 1000 transmission? ›

The Allison 1000 Transmission Oil Pump is generally reliable, but begins to lose efficiency very early in life and it's struggle to produce pressure quickly begins to scale as it ages. The Allison's central pump gears work similar to how most engine oil pumps work; two gears, one residing inside the other.

How do I know if my Allison Transmission is bad? ›

Loud, unnatural sounds could mean that your Allison transmission needs maintenance or replacing.
Some of the most common red flags could be:
  1. Slow response time.
  2. Leaks.
  3. Warning lights.
  4. Clunking or grinding.
Jul 12, 2019

Is the new Allison 10-speed any good? ›

The 10L1000 was introduced in 2020. It replaced the Allison LCT 1000, which has been around for more than 20 years. The LCT 1000 is an excellent transmission with an excellent reputation, rooted in the customer's belief that they own the best transmission on the market.

What is the best 10-speed transmission? ›

All of the effort put into the building and design of the 10R80, giving it the feel of a more traditional transmission with the perks of performance and efficiency found in a CVT, makes it the best ten-speed transmission available today.


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