Engage Gear Range, Function - GF27.60-D-3009HAG

TRANSMISSION 722.9 in MODEL 906 

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) 

When the selector lever is at position "N", multidisk brake B3 and multidisk clutch K3 are engaged. When the transmission is shifted from position "N" to position "D" at the ESM control unit (N15/5), the feed to multidisk brake B2 is enabled by the selector valve. The control unit (Y3/8n4) actuates the brake B2 control solenoid valve (Y3/8y6), and multidisk brake B2 is filled with oil.

From the RPM difference (actual slip) between engine speed and turbine speed, the control unit detects whether multidisk brake B2 is full.

The brake B2 control solenoid valve actuates regulating valve B2 and BR which converts the applied working pressure into shift pressure and passes it on to multidisk brake B2. The required slip (specified slip) for the respective gear is stored in the control unit. 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 control unit is reached.

No power in gear range "D" 

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 t110 °C
  • Coolant temperature of 0 °C t120 °C
  • Accelerator pedal not applied
  • Engine speed n < 1000 RPM
  • Braking torque is at least 250 Nm and brake light switch (S9/1) is actuated
  • Transmission's internal calculation of incline is < 18 %
  • 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

Function sequence for "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 and t < 10 °C
• Coolant temperature t > 120 °C and t < 0 °C
• Accelerator pedal applied
• Engine speed n > 1000 RPM
• Braking torque < 250 Nm or brake light switch not actuated
• Transmission's internal calculation of incline is > 25 %
• A touch shift operation has been detected or the selector lever has been shifted from selector lever position "D" to "N", "R", or "P"
• A VGS system fault is detected

Electronic selector lever module control unit, component description	N15/5	GF27.19-D-5300H
Fully integrated transmission control unit, component description	Y3/8n4	GF27.60-D-5165HAG
Component description for brake light switch	S9/1 Model 906.111/113/131/133/135/153/155/211/213/231/233/235/253/255/611/613/631/633/635/637/653/655/657/711/713/731/733/735	GF42.10-D-2010H
B2 multidisk brake control solenoid valve, component description	Y3/8y6	GF27.19-D-5175HAG