GF27.60-P-4014CW Shifting N to D (1St Gear), Function

GF27.60-P-4014CW Shifting N to D (1st gear), function
- TRANSMISSION 722.6











Starting situation:
^ Electronic selector lever module control unit (N15/5) in position "N" or "P"
^ Circuit 61 OFF
^ No pressure in hydraulic system
^ All valves in the shift plate in neutral position

Aim
^ To engage 1st gear with program "S" selected
^ Engage 2nd gear with program "C" selected

Function

Start engine
The working pressure reaches the multidisk clutch via the ball valve (33a)K3 and the end face of the 3-4 shift pressure shift valve via the 3-4 command valve. The 3-4 shift pressure shift valve is switched against the force of the spring towards the right. The 3-4 gearshift solenoid valve is energized simultaneously.

As a result shift valve pressure reaches into the spring chamber of the shift valve B2 and onto the end face of the 3-4 command valve. The shift valve B2 is held in the upper position and the 3-4 command valve shifts to the right.

The working pressure is replaced by the shift valve pressure on the end face of the 3-4 shift pressure shift valve.
(See picture "circuit 61 ON".)

Shift electronic selector lever module from "N" to "D"
The selector valve opens the shift pressure feed connection from the ball valve (33b) with the shift valve B2. In the upper position of the shift valve B2 the shift pressure is applied behind the piston of the multi-disk brake B2 and simultaneously to the mating surface of the piston of the multi-disk brake B2. The multi-disk brake B2 then starts to close. (See "Activation sequence active" picture)

The compression on the opposite surface of the piston of the multidisk brake B2 causes multidisk brake to be connected gently B2.

The electronic transmission control control unit (N15/3) monitors the engagement process via the reduced rotational speed of the drive shaft which is decelerated as the frictional connection of the multidisk brake increases B2. With a corresponding rpm drop the electronic transmission control control unit switches off the current to the 3-4 shift solenoid valve. The spring chamber of the shift valve B2 is unpressurized and switches downwards. As a result the line to the opposite surface of the piston of the multidisk brake B2 is connected to the pressure holding valve. The pressure on the opposite surface of the multidisk brake B2 drops to a residual pressure.

The 3-4 command valve switches to the left. Working pressure reaches the piston of the multidisk brake via the 3-4 holding pressure shift valve and 3-4 command valve B2.

The activation sequence is complete; 1st gear is engaged. (See picture "1st gear engaged").

Shift electronic selector lever module from "N" to "R"
The selector valve opens the connection of the shift pressure supply with the multidisk brake B3. The further sequence of the switch-on process corresponds to the sequence when connecting the multidisk brake B2.

No opposite surface on the piston of the multidisk brake B3.

Residual pressure
The line system remains filled with oil in the steady-state mode of the automatic transmission. As a result no air can enter the hydraulic system and reduce the shift quality.