What is the Detroit DT12 On-Highway?
DT12 On-Highway is Detroit’s 12-speed automated manual offering for highway work. Freightliner distinguishes it from the DT12 Vocational version while identifying both as automated manuals. A transmission that changes gears automatically is not necessarily a torque-converter automatic.
What matters in a comparison
When comparing a DT12 highway tractor, obtain the full transmission code and engine pairing. Evaluate gearing with tyre size and typical loads. Ask which driver controls and software features are actually configured, and review service history for the unit. If the job includes regular site work or substantial auxiliary loads, have that duty assessed explicitly rather than extrapolating from a highway application.
Fluids & filters
Detroit DT12 service-fluid guidance, November 2024; identify Classic/CO2/C/D gearbox generation from the transmission tag.
Reference checked:
Identify the unit first
Use these details to match the manufacturer's application record before choosing a fluid or ordering a filter.
- Full DT12 tag code and serial number
- Gearbox generation, including whether Classic
- Transmission model year, not only chassis year
- Cooler/PTO configuration and service duty
Fluid specifications
Transmission lubricant
Detroit-approved MB 235.16 SAE 75W-85.
2017-and-newer specification DT12 units only. Not approved for Classic/2016-and-older specification transmissions.
Source 1 ↗Transmission lubricant
Detroit-approved MB 235.11 SAE 75W-90.
Approved service fill for Classic/2016-and-older and 2017-and-newer specification DT12 units.
Source 1 ↗Filter numbers & cross-references
A catalogue cross-reference links part numbers. It does not confirm that either part fits every version of this model. Match the original part to the unit first, then check the replacement manufacturer's application and any supersession.
No application-specific filter number is verified here. Use the official identification and parts references below.
Official service and parts reference ↗
What still needs unit-specific confirmation
- Some Classic DT12 units were built in 2017; verify the gearbox generation before selecting oil.
- No universal DT12 oil-filter or screen part number has been verified for this family page. Obtain the exact service procedure and part number through DTNA/Detroit using the transmission tag.
Official service and parts references
Source 1 ↗ Source 2 ↗Follow the current manufacturer's manual for the identified unit. This page does not set a drain interval, fill quantity or repair procedure.
Questions to take to the supplier
- Which DT12 On-Highway variant is fitted?
- What engine and gearing combination was approved?
- Does the proposed job include duty outside ordinary highway use?
Sources & limits
Manufacturer material supports the identification and overview above. Comparison considerations and supplier questions are Truck University’s original editorial interpretation, prepared with AI assistance. They are not an independent performance test or expert inspection.
Model-family reference only. Availability, specifications and service requirements can differ by year, market and configuration. Verify the actual vehicle or component using its identification and current manufacturer documentation. Do not use this page as a parts-fitment, modification, repair or loading instruction.
Published specifications and examples retain their labelled units; the header preferences apply to calculators.
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