Working/lubrication/shift pressure, function - GF27.60-P-3024AHO

TRANSMISSION 724.2 in MODEL 212 

Function requirements for working/lubrication/shift pressure, general 

• Circuit 87 (connected circuit 15) ON
• Oil pressure generation through the primary pump and/or electric transmission oil pump (M42) ON

Working/lubrication/shift pressure, general 

The oil pressures are separated into:

• Working pressure 
• Lubrication pressure 
• Shift pressure 

Working pressure 

The oil pressure produced by the oil pump is converted into working pressure by the working pressure regulating valve.

The level of working pressure depends on the position of the regulating valve and therefore on its geometry.

The position of the working pressure regulating valve is influenced by the working pressure control solenoid valve (Y3/8y1) depending on load and gear. All other pressures required for transmission control are derived from the working pressures.

The optimized working-pressure reduction for the new automatic transmission generation enables lower braking power and therefore reduces the fuel consumption.

Lubrication pressure 

At the working pressure regulating valve, excess oil is diverted to the lubrication pressure regulating valve and from there used in a regulated manner for lubrication and cooling of the mechanical transmission parts and wet clutch.

The pressure in the wet clutch is also limited by the amount of lubrication pressure.

Shift pressure 

The shift pressure (pressure in the multidisk clutch or in multidisk brake) is derived from the working pressure.

The respective control solenoid valve influences the position of the associated regulating valve. In turn the position influences the pressure prevailing in the multidisk brake or in multidisk clutch. The pressure thus depends on the geometry of the respective regulating valve.

The electric transmission oil pump safeguards the hydraulic system's oil supply when the internal combustion engine has stopped running. It is dependent on the transmission oil temperature, the required volumetric flow and activated for coast down shifting. It is actuated by the fully integrated transmission control unit (Y3/8n4).