DT12 On-Highway Series: Automated Manual Transmissions

More Choice. Maximum Efficiency. 

The DT12® On-Highway Series of automated manual transmissions builds upon the DT12’s proven reputation to provide a trio of purpose-built solutions for on-highway applications. All three models offer:

  • Cutting-edge performance
  • Enhanced fuel efficiency
  • Ease of operation for driver comfort
Warranty and Support Watch Video






Max Input Torque (lb-ft)




Overall Ratio




GCW Limit (lbs)





12 forward, 4 reverse

12 forward, 4 reverse

12 forward, 4 reverse

Engine Compatibility

DD13, DD15, DD16

DD13, DD15


Truck Model Availability

Freightliner Cascadia, Western Star 57X, Freightliner M2 112 Plus

Freightliner Cascadia

Freightliner Cascadia, Western Star 57X, Freightliner M2 112 Plus, Freightliner 114SD Plus

Key Feature

Designed for maximum efficiency. New design features enable further downspeeding. Increased GCW ratings and durability allow for improved on-highway capabilities.

Industry-leading AMT. Built for versatility, offering proven performance and fuel efficiency.

Built to maximize weight savings for weight-sensitive applications - up to 125 lbs lighter than the other models.


Ultimate Efficiency: The New DT12-HE

The Detroit® DT12® HE transmission is an all-new, extremely efficient option for those customers looking to reduce fuel consumption as much as possible. The DT12-HE is built for customers who demand the ultimate performance from their transmission. Design enhancements include:

Integrated Detroit Powertrain


The Integrated Detroit® Powertrain delivers the performance and dependability you need to run your business efficiently. Detroit has designed, engineered and manufactured the engine, transmission and axles to work together seamlessly, providing the optimal powertrain solution for your business needs. The Integrated Detroit Powertrain is available in the Freightliner Cascadia.


  • Integrated Communications Benefits: The DT12® transmission links engine to axles, and communicates with the DD13® Gen 5 and DD15® Gen 5 on an integrated electronics network to share damage-reducing information such as clutch overloading and driveline protection.
  • Super-Finished Gears: Tightly-spaced 12-speed gearing, now with "super-finished" gears in the new DT12® available for the Cascadia, improves low-speed maneuverability, making the Detroit Powertrain not only strong and efficient, but also smooth and safe to operate as well.
  • Intelligent Powertrain Management (IPM): The DT12 uses GPS technology and information from a topographical map to manipulate both engine and transmission functions, taking advantage of the truck's surroundings. IPM6 refines the parameters of this technology, making the truck even more capable of utilizing its surroundings efficiently.
  • Transmission Benefits: The DT12's direct drive and over drive gearing, along with eCoast, are integrated with the downsped engine — which now idles at a lower 500RPM when off-throttle — for optimized fuel economy.



  • 2021 Greenhouse Gas-Compliant Engines: The flagship DD13® Gen 5 and DD15® Gen 5 engines are compliant 2021 Greenhouse Gas (GHG21) standards.
  • Downsped Engines = Improved Fuel Economy: The DD13 Gen 5 and DD15 Gen 5 with downsped 400 HP and 1750 lb/ft rating deliver greater horsepower and torque at lower RPMs, keeping your truck in top gear longer while cruising at more efficient engine speeds. Lower engine speeds reduce the number of fuel injections, dramatically improving fuel economy.
  • Six-Blade Engine Fan: The six-blade fan reduces power draw without sacrificing cooling capabilities.

Steer Axle

  • Numerous Steer Axle Advantages: Detroit steer axles offer rugged strength in a lightweight package, and integrate optimally with the other components. They are designed for the life of the axle, with multiple ratings available for tailored weight distribution.
  • Superior Maneuverability: The Detroit Powertrain's state-of-the-art steer axles provide a 55-degree wheel cut for remarkably nimble maneuvering. 
  • Needle Bearings Improve Durability: With needle bearings instead of bushings, they won't damage the king pins, and offer increased durability.

Tandem Rear Axle

  • New Axles Designed for Fuel Economy: To provide optimum efficiency and performance, the Detroit Powertrain includes an all-new axle specifically designed to integrate with the downsped DD13® Gen 5, DD15® Gen 5 and DT12®, resulting in rock-solid reliability and durability.
  • Faster 6x4 Axle Ratios: The 6x4 configuration is available for applications requiring 4-wheel drive and superior traction. A variety of faster axle ratios are available, ranging from 2.41 to 2.28.
  • Faster 6x2 Axle Ratios: The 6x2 configuration boasts a 2.28 ratio, allowing the DD15 Gen 5  to turn lower RPMs with the truck cruising at the same speed. It pairs perfectly with the low RPM torque curve and direct drive transmission. This means it can cruise in top gear longer, for better fuel efficiency.
  • Lighter 6x2 Axle: The 6x2 axle configuration incorporates a non-driven tag axle on the tandem, reducing total weight (by 380 lbs) and the number of moving parts, delivering better fuel economy.
  • New Optional Axle Lubrication Management (ALM): The tandem rear axles feature an optional axle lubrication management (ALM) system that actively regulates the oil level at the ring gear and friction-loss optimized pinion bearings to reduce friction and parasitic loss, extending gear life and further improving fuel efficiency.



  • 1-Box®The 1-Box is a complete aftertreatment emissions system that combines the SCR catalyst, the Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF) and Diesel Exhaust Fluid (DEF) all into one simple component.

The AMT Difference

 An automated manual transmission (AMT) offers the benefits of both a manual and automatic transmission. Its design uses an efficient clutch instead of a torque converter, but the clutch and shifting are handled by a computer-controlled air system. Even a novice driver can get to work with minimal effort and fuel—and maximum productivity.

The DT12® On-Highway Series transmissions provide 12 speeds for increased efficiency and flexibility. Its two-pedal design allows the driver to focus on what’s ahead instead of what’s underfoot, increasing safety and productivity. As a bonus, seamless integration with Detroit® engines and safety systems promotes optimal performance.

DT12 Explorer

Click through the tabs below to learn more about the DT12 features and benefits. 


Transmission automatically disengages when the vehicle is coasting to help maximize fuel economy.

Skip Shift

The Transmission Control Module (TCM) sends electronic commands to “skip” unnecessary gears, helping increase acceleration to achieve cruising speed quickly and smoothly, and allowing the driver to accelerate in the appropriate “start gear” based on load and grade.

Powertrain Communication

A Common Powertrain Controller (CPC) optimizes high-speed communication between the Motor Control Module and the Transmission Control Module, improving operational efficiency throughout the entire powertrain.

Active Driveline Protection

The Transmission Control Module (TCM) calculates the torque wind-up in the driveline and regulates with engine torque control for enhanced driving comfort and less driveline wear.

Intelligent Powertrain Management

Intelligent Powertrain Management (IPM) pinpoints the truck's location and looks over a mile ahead to anticipate terrain. IPM will adjust cruise control, pre-select gears, eCoast and brake the engine to maximize efficiency into the road conditions ahead.

Total Weight

The aluminum housing and single countershaft help save weight, allowing for even more payload efficiency, while still offering excellent durability.

Power Take-Off

DT12® transmissions are available with a proprietary rear-mount-only Power Take-Off (PTO) that may allow customers in the bulk-haul tractor/trailer market to operate applications using liquid trailers, dry goods, wet goods, and moving floors.

Truck Model Options

DT12 on-highway series transmissions vary across a range of truck models. 

M2 112 Plus
Western Star
Find A Dealer

Detroit Connect Virtual Technician®

If maintenance issues come up while on the road, you can count on Detroit Connect Virtual Technician remote diagnostics system to let you know how serious the fault code is, as well as where, when and how to fix the issue so you can make informed maintenance decisions and get back on the road faster.

Connect Today

Learn more by visiting the nearest Freightliner or Western Star dealership.

Find Nearest Dealer


Detroit DT12 Brochure Detroit DT12 Driver Card DT12 On-Highway Spec sheet DT12 | On Highway Technical Specs | Detroit


Detroit DT12 Front Image Detroit DT12 Back Image Detroit DT12 Left Profile Image Detroit DT12 Right Profile Image DT12 On-Highway Series Transmission Image DT12 On-Highway Series Transmission Back Image DT12 On-Highway Series Transmission Side Image


Detroit DT12 Fuel Economy Video Detroit DT12 - Freightliner Intro Training Video Detroit DT12 - Freightliner Creep Mode Training Video Detroit DT12 - Freightliner Hill Start Aid Training Video Detroit DT12 - Freightliner Transmission Control Training Video Detroit DT12 - Freightliner Kick Down Training Video Detroit DT12- Freightliner Driving Modes Training Video Detroit DT12 - Freightliner eCoast Training Video Detroit DT12 - Freightliner IPM Training Video Detroit DT12 - Classic Cascadia Descent Control Training Video Detroit DT12 - Freightliner Auto Neutral Training Video Detroit DT12 - Inclement Weather Training Video Detroit DT12 - IPM4 Training Video Detroit DT12 Product Video Detroit New DT12 - IPM and Cascadia Dash Display Training Video Detroit New DT12 - IPM Predictive Acceleration Mode Training Video Detroit New DT12 - IPM Crest Coast Mode Training Video Detroit New DT12 - IPM Steep Hill Crest Coast Mode Training Video Detroit New DT12 - IPM Dip Coast Mode Training Video Detroit New DT12 - IPM Driver Safety Considerations Training Video Detroit DT12 - Freightliner auto neutral  Video Detroit DT12 - Video de formación de Freightliner -  Introduccion Detroit DT12 - Video de entrenamiento de modo de fluencia lenta  - Freightliner Detroit DT12 - Freightliner Ayuda de arranque en subida - Video Detroit DT12 - Freightliner Video de Entrenamiento Sistema Saltado de Cambios Detroit DT12 - Video de entrenamiento de control de la transmisión Freightliner Detroit DT12 - Video de entrenamiento del sistema Kick down de Freightliner Detroit DT12 - Freightliner modos de conducción - video de entrenamiento Detroit DT12 - Video de entrenamiento del sistema Rodado Economico de  Freightliner Detroit DT12 - Video de entrenamiento de frenado del motor Freightliner New DT12-HE Automated Manual Transmission Detroit DT12 - Video de entrenamiento de control de descenso Freightliner Detroit DT12 - Video de entrenamiento -  Inclemencias meteorológicas Detroit New DT12 - Video de entrenamiento de Sobrerevolucion en Descenso Detroit DT12 - Cascadia Descent Control Training Video Detroit New DT12 - Video de entrenamiento de Sobrerevolucion en Descenso