Working/Lubrication/Shift Pressure, Function - GF27.60-P-3024ANI

Transmission 725.0 in model 253 

Function requirements, general 

• Terminal 15 ON
• Engine running

Working/lubrication/shift pressure, general 

The oil pressures are separated into:

• Working pressure 
• Lubrication pressure 
• Shift pressure 

Working pressure 

The oil pressure generated by the oil pumps (primary oil pump and electric auxiliary oil pump (M42)) 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 solenoid valve (Y3/8y19) depending on load and gear. All other pressures required for transmission control are derived from the working pressures.

Fuel consumption-reducing and comfort-enhancing measures at the automatic transmission:

The optimized working-pressure reduction enables lower braking power and therefore reduces the fuel consumption. Fuel consumption can be reduced further and the response time to driver load change requests improved by means of controlled minimum slip at low rpm.

Lubrication pressure 

At the working pressure regulating valve, excess oil is routed to the lubrication pressure regulating valve where it is used to regulate the lubrication and cooling for the mechanical transmission components, and the torque converter (transmission 725.004/008/011/041/044/048/054/058) or the wet clutch (transmission 725.096). Apart from this, the level of lubrication pressure for the pressure in the torque converter (transmission 725.004/008/011/041/044/048/054/058) or the wet clutch (transmission 725.096) is restricted.

Shift pressure 

The shift pressure (pressure in the multidisk clutch or in multidisk brake) is derived from the working pressure. The respective 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 electrical auxiliary oil pump ensures the oil supply of the hydraulic system when the combustion engine is switched off. It is dependent on the transmission oil temperature and the required volumetric flow rate. Actuation is performed via the fully integrated transmission control unit (Y3/8n4).