Torque Assist

An intelligent hydrostatic CVT for trailers and towed implements.

Current systems that drive the wheels of a trailer have many uncontested advantages but several limitations as well. They are usually completely mechanical one- or two-speed transmissions –often without freewheeling– or hydrostatic drives that use large one- or two-speed radial piston motors without planetary wheel reducers. When powered by the tractor’s pump they achieve relatively low torques and can’t use the full potential of the tractor’s hydraulics. PGAC solves these limitations with Torque Assist, an intelligent continuously variable transmission with freewheeling for trailers and towed implements.

Because of its modular design, each implement or trailer between 1 up to 33 tons can be fitted with the optimal hydrostatic transmission with a stepless variable speed between 300m/h up to 12km/h, a power between 1 up to 250kW, with a very high torque and patented freewheeling.


Our axles have two integrated wheel reducers and two integrated variable axial piston motors. They are powered by the tractor’s pump and controlled electronically with a touch screen. You can activate Torque Assist while driving forward or in reverse, and set the tractive effort. Tractive effort is enabled when you’re driving slower than the critical speed. When driving faster than the critical speed, Torque Assist freewheels so there are no losses due to back driving, and the components are protected from wear and overspeed. By using variable displacement hydromotors the speed of the tractor is automatically followed while the full power of the tractor’s pump can be used, driving forward and in reverse. When wheels slip the torque of only these wheels is reduced by torque vectoring. Additionally while turning, the torque on the outer wheels is increased, to decrease the turn radius without the need to activate clutches or braking. Optionally Torque Assist is available with hydraulic retarding for machines operating in mountainous areas.

Benefits of Torque Assist:

  • Flexible modular design allows for tailoring to your needs and machines.
  • Increases productivity.
    • Reduces down-time. Very high torques (up to 30.000 Nm/wheel), also when powered by the tractor’s pump, are achieved by the wheel reducers. By using variable hydromotors the full power of the pump can be used independent of the speed. This allows you to drive with Torque Assist where others get stuck.
    • Diminishes damage to the soil or turf by smaller tire tracks, reduced soil compaction and reducing slip.
  • Decreases operational costs by saving fuel and reducing wear through:
    • The unique patented freewheeling, achieved in the wheel reducers.
    • Eliminating the need for ballast.
    • Reducing slip.
    • The same load can be trailed by a smaller tractor.
    • Relieving the tractor’s drivetrain.
  • Easy and safe to control. You can concentrate on the most important task at hand, while the following tasks are automated:
    • Following the speed of the tractor.
    • Torque vectoring to improve tractive effort, stability, and handling.
    • Disabling tractive effort when the tractor brakes to increase safety and reduce wear.
    • Protecting components against overspeed and oil-shortage.
  • Designed for tractor hydraulics; no extra pump, speed increasing gearbox, cooler, or reservoir needed.