Allison Transmission AT, MT, HT Series ON-Highway transmission

Online pdf Allison Transmission AT, MT, HT Series ON-Highway transmission

A BRIEF DESCRIPTION OF THE ALLISON AUTOMATIC
Allison automatics described in this manual include a hydraulic torque converter, a planetary gear train, and a hydraulic control system which supplies fluid under pressure to apply the clutches and automatically shift ranges.

The torque converter multiplies engine torque during starts and acts as a hydraulic cushion between the engine and gearing. The clutches and gear sets provide multiple speeds forward and one speed reverse.

The torque converter lockup clutch, for maximum fuel economy, engages automatically after the vehicle is moving. All models in this manual, except AT 500, have a lockup clutch.

TORQUE CONVERTER
The torque converter consists of three elements — pump, turbine, and stator. The pump is the input element and is driven by the engine. The turbine is the output element and is driven by fluid from the pump, or directly by the pump when the lockup clutch is engaged. The stator is the reaction (torque multiplying) element.

The torque converter is continuously filled with fluid. The pump, driven by the engine, directs the fluid against the turbine vanes, which causes the turbine to rotate. The turbine returns the fluid through the stator, which redirects the flow so that fluid strikes the pump vanes in the same direction that the pump is rotating. As the pump turns faster in relation to the turbine, the velocity of the fluid increases and so does the torque multiplication.

As the speed of the turbine approaches the speed of the pump, the fluid flow starts striking the back sides of the stator vanes. This causes the stator to freewheel in the same direction as the pump and turbine. When this occurs, the torque multiplication stops and the converter functions as a fluid coupling.

Allison Transmission AT, MT, HT Series ON-Highway transmission For Free

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