Sectioned model of a heavy-duty automatic transmission, designed for technical and vocational automotive training. It features a torque converter with lock-up clutch, hydrodynamic retarder, rotating multi-disc clutches, fixed-position multi-disc brakes, and an oil cooler with an oil-water exchanger. The gearbox is operated manually through a crank handle, allowing for detailed observation of gear shifting, torque flow, and braking mechanisms. Mounted on a wheeled stand for mobility, this trainer provides practical insights into the inner workings of heavy truck automatic transmissions.