Hydraulic Control Unit

Hydraulic control unit
General

A control unit is required to enable the mechanical power transmission system to operate. An hydraulic control unit is used for this purpose.

The unit consists basically of an oil pump and an electronically controlled valve assembly.

In the hydraulic control unit for the AW 30-40/43 transmissions, certain components have been replaced by electromechanical solenoid valves which, in turn, are controlled by the TCM. A kickdown cable and governor are omitted for the same reason.

Hydraulic oil pump

The pump - a conventional gear-type unit which runs as soon as the engine is started - is driven by the torque converter pump hub.

The unit consists of a split pump housing, drive gear and pump runner.

The pump draws fluid from the pan through a strainer and delivers it at controlled pressure to the various transmission components. This pressure, which is also influenced by solenoid valve (STH) under the control of the TCM, is known as the line pressure.