GF27.60-P-3009AHZ Engage Gear Range, Function
GF27.60-P-3009AHZ Engage gear range, function
- Transmission 722.902/903/904/906/907 [model 164.1]
- Transmission 722.902/903/904 [model 164.8]
- Transmission 722.902/904/906/999 [model 251.1]
Function requirements for gear range engagement, general
^ Circuit 87 ON
^ Circuit 61 ON
Gear range engagement general
Each gear change is triggered by the fully integrated transmission control (VGS). In the process one component group is assigned to each shift operation.
One component group consists of the respective control solenoid valve, regulating valve involved, shift valve responsible and the required multidisk brake or multidisk clutch.
The pressure in the multidisk brake or multidisk clutch to be engaged is increased constantly while at the same time the pressure in the multidisk brake or multidisk clutch to be disengaged is reduced. The process is a smooth transition and the components affected are actuated directly. This makes it possible to downshift, even through several gears.
Gear range engagement, function sequence
Shifting "N" to "D" (1st gear)
In position "N" of the DIRECT SELECT gear selector switch (S16/13), multidisk brake B3 and multidisk clutch K3 are engaged. When the intelligent servo module for DIRECT SELECT (A80) shifts from position "N" to position "D", the feed to multidisk brake B2 is enabled by the selector valve. The fully integrated transmission control unit (VGS) (Y3/8n4) actuates brake control solenoid valve B2 (VGS) (Y3/8y6) and multidisk brake B2 is filled with oil.
By the rpm difference (actual slip) between the engine speed and turbine speed the fully integrated transmission control unit (VGS) detects whether the multidisk brake B2 is full.
The brake control solenoid valve B2 (VGS) actuates the regulating valve B2 and BR which converts the adjacent working pressure into shift pressure and passes it on to the multidisk brake B2
In the fully integrated transmission control unit (VGS), the required slip (specified slip) is stored for the respective gear. Depending on the specified slip, the control pressure on regulating valves B2 and BR is changed via brake control solenoid valve B2 (VGS).
The pressure in multidisk brake B2 is changed until the specified slip stored in the fully integrated transmission control unit (VGS) is reached.
The shift pressure produced by the regulating valve B2 and BR depends on the geometry of the regulating valve B2 and BR.
"No power" function sequence in gear range "D" on model 164 and model 251 in combination with engine 642 as of 5.1.2009
Function requirements
^ The vehicle speed v = approx. 15 km/h must be exceeded once after engaging the selector switch position "D".
^ The "no power" function sequence in gear range "D" is activated in the DIRECT SELECT gear selector switch position "D" if the following conditions are met:
- The driver has braked the vehicle to a standstill
- Transmission temperature in range from 10 degrees C to 110 degrees C
- Coolant temperature in the range from 0 degrees C to 120 degrees C
- Accelerator pedal not actuated
- Engine speed in range of 570 rpm to 1000 rpm
- Braking torque is at least 250 Nm and brake light switch (S9/1) is actuated
- Transmission-internal uphill slope calculation value less than 18 %
- Transmission mode "C" or "S" selected
- 1st gear engaged by fully integrated transmission control and no off-road gear, or the Offroad-Program button (N72/1s25) is not active
- VGS operating without faults
Function sequence
The VGS reduces the flow at the brake control solenoid valve B2 (VGS) in such a way that the shift pressure is reduced to the back pressure spring level via the regulating valve B2 and BR and the multidisk brake B2 is converted to a regulated slip. This reduces the transmission output torque when the vehicle is stationary and reduces consumption.
The function sequence of "no power" in gear range "D" is deactivated when at least one of the following conditions is met:
- Vehicle speed v greater than 0 km/h
- Transmission oil temperature t greater than 110 degrees C
- Coolant temperature t greater than 120 degrees C
- Accelerator pedal actuated
- Engine speed n less than 570 rpm or n greater than 1000 rpm
- Braking torque less than 250 Nm or brake light switch not actuated
- Transmission-internal uphill slope calculation value greater than 25 %
- A touch shift operation was detected or the DIRECT SELECT gear selector switch was switched out of gear selector switch position "D" to "N", "R", or "P"
- A VGS system fault was detected
