Drivetrain options · 3 of 4 · Eaton
Eaton heavy-duty 4-speed EV transmission
Eaton sells components rather than complete systems. Its heavy-duty 4-speed EV transmission sits behind a central electric motor and keeps the vehicle’s driveshaft and rear axle, which makes it the most retrofit-shaped part in this comparison.
- System
- Eaton 4-speed EV
- Type
- Gearbox behind central motor
- Keeps C12 + MH 4000?
- No (keeps driveshaft + axle)
- Battery (supplier)
- Builder’s choice
- High voltage
- Builder’s choice
- Sold for retrofit?
- Not public
- Coach fit
- Possible component
Tested against a 2002 Country Coach Magna: 40 ft, tag axle, Cat C12 (about 425–505 hp, up to about 1,550 lb-ft) and an Allison MH 4000.
In plain terms
What Eaton offers, and why it matters for a coach
In a central-motor layout the diesel engine and automatic transmission come out, and an electric motor with a multi-speed gearbox takes their place in the engine bay. The driveshaft, rear axle and tag axle stay. Eaton’s gearbox gives a smaller motor a deep first gear for launching and climbing, which matters for a coach that weighs as much as a loaded truck.
Eaton publishes detailed specifications: input torque, ratios, dry weight, oil capacity and a rear power take-off. It also sells high-voltage DC-DC converters that turn traction-battery power into 12 or 24 V for the chassis and house, one of the few house-power parts in this comparison with published ratings.
What Eaton does not supply is everything else: the motor, inverter, battery, controls and the integration work. The heavy-duty 4-speed is also new, launched in 2024, and its maintenance intervals are still listed as “TBD”.
01 · How it works
How it works
A 4-speed EV gearbox that lets a smaller motor move a heavy load
Eaton makes components, not complete systems. Its heavy-duty 4-speed EV transmission sits behind one central electric motor, roughly where the engine and transmission were, and keeps the driveshaft and rear axle. A deep first gear helps a smaller motor launch and climb.
| Max input torque | 2,600 N·m (about 1,920 lb-ft) |
|---|---|
| Max input speed | 5,000 rpm |
| Ratios | 5.88 · 3.30 · 1.82 · 1.00 |
| Dry weight | 192 kg (423 lb), 650 mm long |
| Oil | 7 L, cooler-less operation |
| PTO | Rear PTO, up to 700 N·m continuous |
| Controls | 12 or 24 V control module |
The Eaton Cummins joint venture builds the Endurant automated transmissions for diesel trucks. Eaton sold a parallel diesel-electric hybrid for medium-duty trucks until 2014.
Sources: Eaton HD 4-speed EV transmission · PTO installation guide · Installation guide TRIG2200
02 · Advantages & disadvantages
Advantages & disadvantages
The most retrofit-shaped part, if you build the rest yourself
Advantages
- Keeps the coach’s driveshaft and rear axle; a central motor + 4-speed takes the place of the C12 and MH 4000.
- Maker claim extends range or allows a smaller battery, and improves grade climbing with a smaller motor.
- Light (423 lb) with a PTO for accessories; Eaton also sells HV DC-DC converters.
Disadvantages
- Motor, inverter, battery, controls and integration all come from others.
- 2,600 N·m input limit: the motor must be matched to a 40,000+ lb coach.
- Eaton left the North American hybrid market in 2014, citing weak demand. Heavy-duty 4-speed is new (launched in 2024); maintenance intervals still listed as “TBD”.
Sources: Eaton interview, SAE 2025 · NREL UPS study · HDT: Eaton exits hybrid · Eaton–Proterra · ZX5 spec
03 · Feasibility for a Magna-type coach
Feasibility for a Magna-type coach
in a central-motor or series-hybrid design. Small-volume sales to converters Not public.
The practical takeaway: in a central-motor or series-hybrid rebuild, Eaton’s gearbox and DC-DC converters are realistic building blocks. The motor has to be matched to a 40,000 lb-plus coach within the gearbox’s input-torque limit, and the integration would be custom engineering.
04 · Maintenance
Maintenance
- 7 L of oil, no external cooler or lubrication system required; maintenance intervals “TBD” on Eaton’s spec sheet.
- Diagnostics through Eaton ServiceRanger; Eaton’s established transmission service network, though EV-specific service coverage is Not public.
- Recalls or field actions for the HD 4-speed: none found in our search.
- The motor, inverter and battery carry their own makers’ service and HV training requirements.
Sources: Eaton spec page · TRIG2200 · Service manual TRSM2200
05 · Installation in a 40-ft pusher
Installation in a 40-ft pusher
What a conversion would involve in a 40-ft, tag-axle diesel pusher such as a 2002 Country Coach Magna (Cat C12, Allison MH 4000). Figures are only given where a source publishes them.
- Space: motor + gearbox in the rear engine bay where the C12 and MH 4000 sit; pack in basement bays and the freed engine space.
- Weight: gearbox 423 lb; motor and inverter depend on supplier Not public; battery about 20 lb/kWh Estimate. Removing the C12, MH 4000, fuel and cooling offsets part of this.
- Electrical: transmission control module runs on 12 or 24 V. HV voltage set by the chosen motor and pack.
- Labor: Not public; custom adapter, mounts, driveshaft length and controls work.
06 · 12 V house power & coach batteries
12 V house power & coach batteries
Eaton sells the converter that makes 12 V from an EV pack
12/24 V from high voltage
Eaton’s HV DC/DC family replaces the alternator: 800 V → 14 V at 3 or 5 kW (214–357 A), 800 V → 28 V at 5 or 10 kW, 400 V → 14 V at 3 kW. Liquid-cooled, up to 95% efficient; input 500–850 V for the 800 V models. Bi-directional versions are optional.
Traction pack as house bank?
Possible in a central-motor build, because the builder picks the pack. Keep a separate isolated 12 V battery for starting, BMS and contactors; size the pack so camping use doesn’t cut into the reserve needed to drive. Estimate a 5 kW 12 V converter covers chassis loads plus a large 12 V house panel.
AC power & inverters
Eaton’s transmission doesn’t export AC. The rear PTO (700 N·m) could drive an accessory generator, but a separate 120/240 V split-phase inverter is the cleaner route. Estimate 6–10 kW for roof A/Cs plus induction; shore power would charge the pack through an onboard charger.
Sources: Eaton HV DC/DC data sheet · xEV4 PTO guide
07 · Cost of ownership
Cost of ownership
price Not public. Independent NREL’s 36-month study of UPS vans with Eaton’s earlier hybrid found 23% better fuel economy and 19% lower fuel cost per mile, but 96.3% uptime against 99.0% for diesel.
08 · Battery & supplier
Battery & supplier
Eaton supplies no traction battery. Example pairing: Proterra ZX5 buses used Eaton’s transmission with 450–675 kWh Proterra packs.
09 · How it compares
How it compares
Eaton in the side-by-side table. The full table, including the parallel PTO add-on, is on the overview.
| System | Type | Keeps C12 + MH 4000? | Battery (supplier) | HV | 12/24 V & AC power | Sold for retrofit? | Coach fit |
|---|---|---|---|---|---|---|---|
| Eaton 4-speed EV | Gearbox behind central motor | No (keeps driveshaft + axle) | Builder’s choice | Builder’s choice | Eaton DC-DC 3–10 kW (12/24 V) | Not public | Possible component |
10 · Sources & credits
Sources & credits
Every figure on this page links back to one of these. Labels:
- Maker claim what the manufacturer says
- Independent government test, public record or trade press
- Estimate typical engineering range, not a measured figure
- Not public no published figure found
- Eaton HD 4-speed EV transmission eaton.com
- PTO installation guide eaton.com
- Installation guide TRIG2200 eaton.com
- Eaton interview, SAE 2025 mobilityengineeringtech.com
- NREL UPS study docs.nlr.gov
- HDT: Eaton exits hybrid truckinginfo.com
- Eaton–Proterra eaton.com
- ZX5 spec valleyregionaltransit.org
- Service manual TRSM2200 eaton.com
- Eaton HV DC/DC data sheet eaton.com
Diagrams are original and simplified, based on the manufacturers’ published specifications. Photo credits and licenses appear under each image. Research compiled October 23, 2026; specifications, prices and availability change.