По всей видимости речь идет о системе дифференциального управления поворотом. Мне такое в жизни не попадалось. На D9 не нашел (трудно искать, не зная модели и серийного номера). Нашел только на D6N
См. вложение:
(1) Power train oil pump
(2) Transfer and bevel gears
(3) Planetary and brake
(4) Accumulator
(5) Transmission hydraulic control
(6) Transmission
(7) Transmission remote taps
(8) Power train oil filter
(9) Brake control valve
(10) Steering differential and brake
(11) Final drives
(12) Power train oil fill and dipstick
(13) Torque converter and brake remote taps
(14) Steering control lever
(15) Torque converter
(16) Temperature Control (17) Power train oil cooler
The basic components of the differential steering system include the following items: a planetary and brake unit, a steering differential and brake unit, a hydraulic steering pump, a hydraulic steering motor and the steering controls. The planetary and brake unit (3) is mounted inside the bevel gear case behind the final drive on the right side of the machine. The steering differential and brake unit (10) is mounted inside the bevel gear case behind the final drive on the left side of the machine. These units transfer power from the bevel gear to the final drives in varying proportions. The input is based on the operator input from the steering control lever. Input from the steering control lever signals the steering pump to send oil to the steering motor. The steering motor acts on the steering differential and brake unit in order to vary the power to each final drive.

Оно?