Oil Supply For Automatic Transmission, Function - GF27.57-D-1000HAG

TRANSMISSION 722.9 in MODEL 906 

Function requirements for automatic transmission oil supply, general 

• "Circuit 87 ON" (connected circuit 15)

Oil supply for automatic transmission, general 

With the combustion engine running, the oil pump (primary pump) delivers oil to the electro hydraulically actuated automatic transmission. The oil pump drive is provided through the torque converter's drive flange. The pump is installed in the transmission bell housing behind the torque converter.

The electric transmission oil pump is actuated via the transmission oil auxiliary pump control unit (N89) when switching the internal combustion engine on and off. When the internal combustion engine is switched off, the electric transmission oil pump takes over the oil supply of the control elements and actuators of the automatic transmission.

Oil supply for automatic transmission with stopped internal combustion engine (with code (MJ7) ECO start) 

If with a stopped internal combustion engine, the oil supply fails, all control elements and actuators switch to an unloaded basic status and the automatic transmission power flow stops.

When the internal combustion engine is started, and the oil supply has been built up, the gear position has to be changed from "N" to "D". The resulting loss of time between the start-off request and the start-off time is reduced by the electric transmission oil pump (M42).

The electric transmission oil pump also supports the primary pump at low internal combustion engine speeds.