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ZF Friedrichshafen 8HP90S – Eight Gears to Tackle Special Applications

Decoupling torsional vibrations induced by the engine in the driveline

ZF is a global leader in driveline and chassis technology as well as active and passive safety technology. The company acquired TRW Automotive on 15 May 2015, which was then integrated within the organisational structure as the Active & Passive Safety Technology Division.

ZF’s 8-speed automatic transmission ZF 8HP has already conquered the passenger car world. In the form of a new special version dubbed ZF 8HP90S special vehicles can also benefit from its long-term qualities: These include fast, comfortable gearshifts, a high total spread, the very good power-to-weight ratio as well as flexible applications and outstanding efficiency.

The ZF engineers focused primarily on two criteria when designing the 8-speed automatic transmission for light special vehicles with four- or six-wheel drive: The ZF 8HP90S must have the same outstanding basic characteristics as its passenger car counterpart and at the same time perform as effectively as possible the new commercial vehicle-specific tasks – regardless of whether this involves a fire truck, vehicles used in agriculture and forestry or municipal vehicles.

ZF solves this task with the ZF 8HP90S whose basic transmission is designed for input torques of up to 1 000Nm. Its eight gears provide a high total spread of 7.05 with very small gear steps, which also promotes power, comfort, and efficiency in equal measure. Nonetheless the ZF 8HP90S remains a compact lightweight: It is less than 700mm long and tips the scales at just 99kg including oil.

The technical prerequisite comes in the shape of a sophisticated, innovative gearset design with four planetary gearsets and five shift elements. Since there are always only two shift elements open per gear, inner drag losses in the transmission are greatly reduced. The torsion damper system in the torque converter also has a positive impact on shift characteristics, durability and, not least, fuel consumption: This system effectively decouples the torsional vibrations induced by the engine in the driveline. At the same time, the lock-up clutch can also be engaged faster. Overall these measures translate into outstandingly short response and shift times below the human threshold of perception.

As a neutral interface, the ZF 8HP90S comes at the output end with the cross cut commonly used in commercial vehicles to connect standardized propshafts. Added to which are unified connections: In terms of the mechanical components, this entails the SAE 4 engine interface; the SAE CAN J1939, J1939-14, or J2284 communications buses are available for the electronics. The actual hardware and software on the ZF 8HP90S are fully integrated in the transmission, which minimizes the wiring required.

For further information please visit: www.zf.com/special-transmission.


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