MINING TRUCKS
Sigma Powertrain completes heavy duty TERRAMAX™ design
After years of development and in-depth design work, Sigma Powertrain has completed the design of its TERRAMAX™ heavyduty electric powertrain platform and released the design for production hardware. The first TERRAMAX units are now being built for deployment in 2026. Designed specifically for the world’ s most demanding duty cycles, mining trucks are one of the main target markets.
For mining applications, TERRAMAX enables OEMs and retrofit partners to retain proven axle and differential systems while electrifying the vehicle with a robust, serviceable, and highly efficient powertrain.
John Kimes, President and CEO of Sigma Powertrain, told IM:“ We are building 10 TERRAMAX gearboxes this year for field use and are talking to several retrofit partners. This solution is highly significant for the mining market. Today, we believe we are the only company with a practical conversion architecture for mechanical haul trucks from the CAT 777 through the CAT 793- and their equivalent counterpart models from Komatsu and Hitachi- that allows the existing rear axle and differential package to remain in place. TERRAMAX replaces the OEM transmission while keeping the powertrain packaged within the suspension envelope of the vehicle.”
At the heart of TERRAMAX is Sigma Powertrain’ s 5-speed heavy-duty electric transmission coupled with high-performance electric drive systems, such as the 1.3 MW Catalyst E-Motor from Dayton Phoenix. Unlike many direct-drive architectures, TERRAMAX uses gear reduction to keep electric machines operating in their most efficient range while delivering the wheel torque required for extreme-duty applications.
Key specifications include up to 2.0 MW of continuous system power, a 5-speed automated transmission, ratios of 13.49, 6.35, 3.67, 1.73 and 1.00, and a design target of more than 30,000 hours of service life.
In hybrid truck applications, Sigma Powertrain estimates fuel savings of more than 40 %. This is achieved through a combination of roughly 15 % from replacing the hydraulic transmission with a high-efficiency mechanical gearbox, 15 % from regenerative braking capability, and 10 % from downsizing the diesel engine and operating it closer to its most efficient range. TERRAMAX is also compatible with battery-electric and hydrogen fuel-cell architectures.
The core advantage is modularity. The same hardened steel transmission backbone can support one or two electric motors, full battery-electric operation, a series-hybrid engine-generator
arrangement, or a parallel-hybrid configuration where diesel power is tied into the driveline through a compact drop box.
For the largest mining platforms, including 2 MW-plus applications such as the CAT 793 class, Sigma Powertrain is also developing a 4-node power-split version of TERRAMAX. This architecture uses the same heavy-duty geartrain philosophy but replaces conventional shift events with a clutchless power-split arrangement. The result is continuous torque delivery to the output- a critical advantage in very high-power haulage and other duty cycles where torque interruption is undesirable.
The 4-node TERRAMAX power-split combines a diesel engine and two electric machines through a mechanical planetary network. Rather than using the diesel only as a generator, the engine remains mechanically connected into the power path while the electric machines control speed, torque balance, boost and regenerative energy capture. This allows the diesel engine to operate near its most efficient point while the electric machines handle transient load, launch torque, grade response and braking energy recovery.
Kimes said:“ For the CAT
The first TERRAMAX units are now being built for deployment in 2026
793 size class, you are no longer talking about a simple electrified gearbox. You need a true power-management system. The 4-node TERRAMAX lets us blend diesel and electric power mechanically, keep continuous torque on the output, recover energy downhill, and keep the engine in its sweet spot. That is the difference between simply replacing a transmission and creating a heavy-duty hybrid powertrain that is purpose-built for mining.”
Sigma Powertrain says the 4-node architecture is especially relevant for applications above 2 MW where full battery-electric operation may not be practical for every duty cycle, but where diesel fuel reduction, regenerative braking and powertrain efficiency still offer major economic and emissions benefits. The company sees this as a bridge between today’ s diesel-mechanical haul trucks and the future of fully electrified mine fleets.
“ The big win is that TERRAMAX does not force the customer into one architecture,” Kimes added.“ A mine can choose batteryelectric, series hybrid, parallel hybrid, or a 4-node power-split hybrid depending on the truck size, route, charging infrastructure and duty cycle. The mechanical backbone stays common, but the energy source can change.”
Sigma Powertrain believes this flexibility gives TERRAMAX a practical advantage in mining retrofit programs, where packaging space, axle retention, serviceability, duty cycle variation and uptime are often more important than simply choosing the highest nameplate power rating. type of terrain with many hills and variation, allows a smaller, cheaper battery to recover significant energy and on average can achieve 25 % to 30 % fuel reduction. The fact that there are no operational plug-in requirements for the truck is also ideal for speeding up the introduction of this new technology, because it doesn’ t put any burden on the mines’ existing infrastructure to set up dedicated charging points. U & M started by developing the battery pack inhouse – there were a lot of learnings in getting the truck ready to integrate with a battery plus dealing with the weight and volume constraints but ultimately, U & M sought a partner with a mature battery technology so it could focus on its core business of productivity testing. It found that in ABB. U & M opted to have the battery on the side of the truck to allow for a standard battery geometry and give easy maintenance access. The ABB LTO battery is not a low cost option but its high performance allowed U & M to use a smaller battery pack which therefore does make it competitive.
International Mining | JULY 2026 55