Engage gear range, function - GF27.60-P-3009AHL

TRANSMISSION 722.9 (except 722.930/931) in MODEL 212 

Function requirements for Engage gear range, general 

• Circuit 87 ON
• Circuit 61 "ON" (engine running)

Engage gear range, 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, the regulating valve involved, the responsible shift valve 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.

Function sequence for engage gear range 

Shifting "N" to "D" (1st gear) 

In position "N" of the DIRECT SELECT selector lever (S16/13), the 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 opened by the selector valve. The fully integrated transmission control unit (Y3/8n4) actuates the multidisk brake control solenoid valve B2 (Y3/8y6) and the multidisk brake B2 is filled with oil.

From the rpm difference (actual slip) of engine speed to turbine speed the fully integrated transmission control unit detects whether the multidisk brake B2 is filled.

The multidisk brake control solenoid valve B2 actuates the regulating valve B2 and brake pressure regulation 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, the required slip (specified slip) is stored for the respective gear. The control pressure on regulating valve B2 and BR is changed via brake control solenoid valve B2 depending on this. The shift pressure produced by the regulating valve B2 and BR depends on the geometry of the regulating valve B2 and BR. The pressure in multidisk brake B2 is changed until the specified slip stored in the fully integrated transmission control unit is reached.

"No power" in gear range "D" for model 212 with engine 276, 642, 651 

Function requirements 

• After selector lever position "D" is engaged, a vehicle speed of v = approx. 15 km/h must be exceeded once.
• The "no power" function sequence in gear range "D" is activated when one of the following conditions is met:
  • Stall protection activated by the VGS (depending on geographic altitude and at low outside temperatures)
  • VGS initiates braked or unbraked coast down shifting from 2nd gear to 1st gear during driving operation
• The function sequence of "no power" in gear range "D" is activated each time the vehicle stops in selector lever position "D" if the following conditions are met:
  • Transmission oil temperature of 10 °C ≥ t ≤ 110 °C
  • Coolant temperature of 0 °C ≥ t ≤ 120 °C
  • Accelerator pedal not applied
  • Engine speed n < 1000 rpm
  • Braking torque is at least 250 Nm and brake light switch (S9/1) operated.
  • Transmission's internal calculation of incline is < 18 %
  • Transmission mode "C" or "E" or "S" selected
  • 1st gear engaged by VGS [fully integrated transmission control]
  • VGS operating without faults

Vehicle standstill can be reached via one of the following conditions:

• Driver brakes the vehicle
• "HOLD function" (Hill Start Assist) is active
• Vehicle is automatically braked by active Distronic (adaptive cruise control) (DTR), on vehicles with code (233) DISTRONIC PLUS

Function sequence of "no power" in gear range "D" 

The VGS deenergizes the brake control solenoid valve B2 so that the shift pressure is reduced via regulating valve B2 and BR and multidisk brake B2 is unpressurized. This reduces the transmission output torque with the vehicle stationary and reduces consumption.

The function sequence of "no power" in gear range "D" is deactivated if the following conditions are met:

• Vehicle speed v > 0 km/h
• Transmission oil temperature t > 110 °C
• Coolant temperature t > 120 °C
• Accelerator pedal applied
• Engine speed n > 1000 rpm
• Braking torque < 250 Nm or brake light switch not operated
• Transmission's internal calculation of incline is > 25 %
• When the vehicle is stopped after a transmission mode change
• A touch shift has been detected or the DIRECT SELECT selector lever has been shifted out of selector lever position "D" into "N" "R", or "P"
• A VGS system fault is detected