Automated manual transmission
Used Detroit DT12 Transmissions
The Detroit DT12 is a 12-speed automated manual transmission found mainly in Freightliner and Western Star trucks with Detroit engines. Send us your tag and VIN details and we search supplier sources for a matching used unit.
Detroit DT12 at a glance
- Type
- Automated manual (AMT), two-pedal
- Forward speeds
- 12
- Versions
- Direct drive and overdrive; vocational variants exist
- Typical applications
- Freightliner Cascadia and Western Star tractors, usually paired with Detroit DD13, DD15 or DD16
Identification tag
How to identify your DT12
The DT12 has an ID label on the transmission housing showing the model designation, serial number and part number. The model designation tells you which DT12 variant you have, including whether it is direct drive or overdrive.
Because the DT12 is closely tied to the truck's Detroit powertrain electronics, the truck VIN is just as important. It lets us check the original build and the engine it was paired with.
01Automated manual, not automatic
The DT12 is a gear-and-clutch transmission with a computer-controlled clutch and shifting. There is no clutch pedal for the driver, but it is not a torque-converter automatic like an Allison.
02Direct drive, overdrive and vocational versions
DT12 variants differ in top-gear ratio and features. Some vocational versions add features for off-road and low-speed work. Swapping to a different variant can change cruise RPM and how the truck behaves, so match the model designation from the label.
03Transmission control unit, software and harness
The DT12 uses a transmission control unit that communicates with the engine and the rest of the truck. A replacement unit may need parameter or software updates with Detroit diagnostic tools, and connectors and harness versions should match. Ask your shop whether the control unit will move over from your old transmission.
04PTO and clutch
If your truck runs a PTO, confirm the replacement is set up for it. The automated clutch and its actuator are part of the system, so note whether you need them with the unit.
05Core and exchange
Core charges or exchange terms may apply depending on the supplier. If they do, they are confirmed on your quote before you commit, along with availability and freight.
Configuration
What we'll ask to match your unit
- What model designation, serial number and part number are on the transmission label?
- Is it a direct drive, overdrive or vocational version?
- What is the truck year, model and VIN?
- Which Detroit engine is it paired with?
- Does the truck use a PTO?
- Do you need the control unit or clutch actuator as well?
FAQ
Detroit DT12 questions
Is the Detroit DT12 an automatic transmission?
No. It is an automated manual transmission. It shifts gears and works the clutch automatically, but inside it is a manual-style gearbox, not a torque-converter automatic.
Can I put a DT12 in a truck that had a manual transmission?
That is a major conversion involving controls, wiring, software and pedals. We focus on like-for-like replacement units.
Does a used DT12 need programming?
Often some setup is needed so the transmission and engine communicate correctly. A shop with Detroit diagnostic software can handle this.
Which trucks use the DT12?
It is most common in Freightliner Cascadia and Western Star trucks with Detroit engines. Your VIN confirms what your truck was built with.
Do you stock DT12 transmissions?
We are an independent sourcing company. We search supplier sources nationwide and confirm availability and freight on your quote.
Related
Ready when you are
Need a Detroit DT12? Send the tag number.
Have your engine serial number or transmission tag and VIN handy. If you don't, we'll help you find them.
Commercial-Engines.com is an independent supplier of used commercial truck engines and transmissions. Manufacturer names, model names and part numbers are used for identification only and do not imply affiliation with, or endorsement by, any manufacturer. Read the full disclaimer.