Detroit DT12 vs Volvo I-Shift
Specs, oil interval and warranty compared
Transmission comparison
The Detroit DT12 and the Volvo I-Shift are both automated manual transmissions, and each comes with its own truck. Detroit lists the DT12 for the Freightliner Cascadia with torque ratings of 2,250, 2,050 and 1,650 lb-ft. Volvo lists the I-Shift for the VNL at up to 1,950 lb-ft. Volvo prints a 5-year, 750,000-mile transmission warranty. The Detroit pages we read do not print one. The oil intervals use different rules, so they cannot be compared one for one. There is no spec-sheet winner.
Figures for DT12 vs I-Shift are taken from the makers' own published documents. Last reviewed November 3, 2026.
DT12 vs I-Shift: side-by-side specs
| Spec | Detroit DT12 | Volvo I-Shift |
|---|---|---|
| Type | Automated manual (AMT) | Automated manual (AMT) |
| Speeds | 12 forward, 4 reverse | 12, 13 or 14 forward; 4 or 6 reverse |
| Torque | 2,250 lb-ft (HE), 2,050 lb-ft (middle), 1,650 lb-ft (HL) | Up to 1,950 lb-ft |
| Weight | Not stated in pounds (the HL is up to 125 lb lighter than the others) | 719 lb (12-speed) or 805 lb (13- and 14-speed), dry, with clutch and oil cooler |
| Gear ratios published | Ranges only: 14.56–0.78 down to 11.64–0.78 in overdrive | Overall ratio range of 14.94:1 to 40.8:1 |
| Fluid | MB 235.16 (75W-85) on 2017 and newer; MB 235.11 (75W-90) on 2016 and older | 75W-90 for overdrive and severe duty; 75W-80 for other automated manual I-Shifts |
| Fluid capacity | About 8.9 qt (2020 C-box); 8.5 or 12.7 qt (2017 B-box and A-box) | About 18 qt or 20.8 qt, depending on the version |
| Oil interval | From 180,000 miles or 3 years (severe) to 400,000 miles or 5 years (line haul up to 80,000 lb); up to 600,000 miles with the Maintenance System | Up to 6 years or 500,000 miles (one interval, no duty split on the page) |
| Warranty as printed by the maker | Not stated on the pages we read | Transmission 5 years or 750,000 miles; clutch 3 years or 350,000 miles (normal duty) |
| Engines the maker names | DD13, DD15, DD16 | D13 |
| Trucks | Freightliner Cascadia, M2 112 Plus, 114SD Plus | Volvo VNL |
Full detail for each transmission: Detroit DT12 guide and Volvo I-Shift guide.
What actually decides DT12 vs I-Shift?
We do not name a winner in DT12 vs I-Shift. There is no independent, like-for-like study of fuel economy or reliability for these transmissions. These are the facts that decide it for a given truck and duty cycle.
- The truck usually picks the transmission
- Detroit lists the DT12 with its own DD engines in Freightliner trucks. Volvo's page names only the D13 for the I-Shift, and our model list shows the I-Shift as the transmission in the VNL. So most buyers are really choosing a truck, not a transmission. If you are weighing the two, you are weighing a Cascadia against a VNL.
- The oil intervals do not line up
- Detroit splits its DT12 intervals by duty and weight, from 180,000 miles for severe work up to 400,000 miles for light line haul. Volvo lists one figure, up to 500,000 miles or 6 years, and does not split it by duty. A bigger number on one page is not proof of a longer-lasting oil. Use the maker's table for your own truck.
- Get the warranty in writing
- Volvo prints its I-Shift terms: 5 years or 750,000 miles on the transmission and 3 years or 350,000 miles on the clutch for normal duty. The Detroit pages we read give no transmission warranty term. Whichever truck you look at, the written coverage on that exact unit beats any general claim.
- Check the fluid by model year or version
- The DT12 uses one oil on 2017 and newer trucks and a different one on 2016 and older. The I-Shift uses 75W-90 in overdrive versions and 75W-80 in the others. Putting the wrong oil in either one is a mistake you can avoid by reading the tag before you buy oil.
Put your DT12 vs I-Shift oil changes on a schedule with the maintenance scheduler. Decode warning lights with the fault code lookup. Before you buy a used truck, run the VIN decoder and the used truck inspection checklist.
More transmission comparisons and guides
DT12 vs I-Shift frequently asked questions
Is the Detroit DT12 better than the Volvo I-Shift?+
Neither maker publishes a failure rate, and there is no independent study that compares the DT12 and the I-Shift. So there is no honest way to name a winner. What the makers publish is different in a few places. The I-Shift lists up to 1,950 lb-ft and a printed 5-year, 750,000-mile warranty. The DT12 lists three ratings up to 2,250 lb-ft and a duty-based oil interval. The practical difference is which truck you are buying.
Does the DT12 or the I-Shift weigh more?+
Volvo lists a dry weight of 719 lb for the 12-speed and 805 lb for the 13- and 14-speed I-Shift. Detroit gives no weight in pounds for the DT12. It only says the DT12-HL is up to 125 lb lighter than the other DT12 models. So there is no weight comparison to make from the maker pages.
Do the DT12 and the I-Shift use the same oil?+
No. The DT12 uses MB 235.16 (75W-85) on 2017 and newer trucks and MB 235.11 (75W-90) on 2016 and older ones. The I-Shift uses Volvo's 75W-90 in overdrive versions and 75W-80 in the others. Volvo says the 75W-80 is not for overdrive I-Shifts and not for automatics such as the Allison.
Can you put a Volvo I-Shift behind a Detroit engine, or the other way round?+
Neither maker's pages describe mixing the two. Volvo's page names only the D13 for the I-Shift. Detroit lists only its own DD13, DD15 and DD16 for the DT12. Treat each transmission as part of its own truck's powertrain.
Which has more gears, the DT12 or the I-Shift?+
The DT12 has 12 forward gears. The I-Shift comes in 12-, 13- and 14-speed versions, so it can have 1 or 2 more. Volvo lists 4 or 6 reverse gears and Detroit lists 4.
Sources for DT12 vs I-Shift
Choosing between DT12 vs I-Shift? Let a dispatcher help.
Grow Trucking finds loads, negotiates rates and does the paperwork for owner-operators and small fleets. Tell us what you haul and we will show you how a DT12 vs I-Shift truck fits the lanes we book.
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Ratings, intervals and warranty terms for DT12 vs I-Shift change by model year and configuration. Confirm exact figures for a specific truck against the makers' current documents and your written warranty before you buy or set a service schedule.
Free tools for a DT12 vs I-Shift decision
Keep a DT12 vs I-Shift truck serviced on time, decode its fault codes and check a truck before you buy.
- Preventive Maintenance SchedulerTrack oil changes for a DT12 vs I-Shift truck by odometer and duty cycle.
- Diesel Fault Code Lookup (SPN/FMI)Decode the SPN/FMI fault codes either DT12 vs I-Shift transmission reports.
- Breakdown Cost EstimatorEstimate what a breakdown costs in repairs and lost revenue on a DT12 vs I-Shift truck.
- Used Truck Inspection ChecklistCheck the transmission and clutch on a DT12 vs I-Shift truck before you buy it used.