Working/Lubrication/Shift Pressure, Function - GF27.60-P-3024ANR
Transmission 725.0 (except 725.096) in model 257, 290
up to model year 2021
Function requirements for working/lubrication/shift pressure, general
- Circuit 15 ON
- Combustion 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 the load and gear involved. 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 diverted to the lubrication pressure regulating valve and from there used in a regulated manner for lubrication and cooling of mechanical transmission parts and the torque converter.
In addition the pressure in the torque converter is limited by the level 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 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. Actuation is performed through the control unit for the fully integrated transmission control electric controller unit (Y3/8n4).
| Overview of system components of automatic transmission (AT) | GF27.10-P-9992ANR |