Mercedes Benz 245 Automatic Transmission Control Unit

The G 320 CDI and G 500 versions are equipped with an electronic 7-speed planetary automatic transmission with touch shift. The transmission has 7 forward gears and 1 reverse gear. The automatic transmission selects the shift operations that best suit the situation and driving style. Gears can be manually selected by briefly touching the gearshift lever in a transverse direction.
The automatic transmission clearly demonstrates its superiority during demanding off-road operations:
• No interruption of power flow during load change and shifting when off-road, on gradients and during trailer operation
Note
The 7-speed planetary automatic transmission is described in the Introduction into Service Manual "Introduction of the New 7-Speed Planetary Automatic Transmission W7A 700".
• Multiplication of starting torque (considerably more power is transferred to the wheels than on a manual transmission due to the characteristics of the torque converter)
• Stress on driver in difficult situations is relieved by automatic gear selection
· 1 Torque converter housing
· 2 Turbine wheel
· 3 Stator
· 4 Impeller
· 5 Transmission housing breather
· 6 Oil pump
· 7 Multidisk brake B1
· 8 Multidisk clutch K1
· 9 Ravigneaux gear set
· 10 Multidisk brake B3
· 11 Single front planetary gear set
· 12 Multidisk clutch K2
· 13 Single rear planetary gear set
· 14 Multidisk brake BR
· 15 Multidisk clutch K3
· 16 Multidisk brake B2
· 17 Park pawl gear
· 18 Pulse ring for rpm sensing
· 19 Ring magnet for rpm sensing
· 20 Ring magnet for rpm sensing
· 21 Electrohydraulic controller unit
· 22 Torque converter lockup clutch
The 2-speed transfer case installed in the G-Class can be switched between 2 gear ratios (on-road ratio, offroad ratio).
The low rotational speed of the drive shafts in off-road mode combined with a high engine torque improves the conditions for traction, particularly on unsurfaced roads.
The integrated interaxle and interwheel differential locks are actuated electropneumatically in the transfer case and electropneumatically/electrohydraulically
in the front axle and rear axle differentials.
· 1 Shift cylinder for differential lock
· 2 Output shaft to front axle
· 3 Differential lock
· 4 Differential
· 5 Output shaft to rear axle
· 6 Speedometer drive
· 7 Intermediate shaft
· 8 Drive shaft
· 9 Synchronizer cone
· 10 Shift fork
Depending on the driving situation, the LOW button can be pressed to switch between the operating modes LOW RANGE (off-road ratio) and HIGH RANGE (onroad ratio). When the LOW button is pressed, a red LED in the button lights up. When the LOW button is pressed again, the LED goes out and HIGH RANGE mode is activated. HIGH RANGE mode is the standard driving mode.
When LOW RANGE is switched on, the engine output pattern and the shift behavior of the automatic transmission are adapted. The specially matched off-road functions of ABS, ESP?? and 4ETS are also activated. In comparison with the HIGH RANGE on-road drive mode, the gear ratio from the engine to the wheels is 1 : 2.5. The drive torque is therefore correspondingly greater.
For the gear ratio change from HIGH to LOW the following conditions must be met:
• Engine speed > 400 rpm
• Vehicle rolling
• Selector lever in position N
• Vehicle speed < 40 km/h (when reversing < 10 km/h)
For the gear ratio change from LOW to HIGH the following conditions must be met:
• Engine speed > 400 rpm
• Vehicle rolling
• Selector lever in position N
• Vehicle speed < 70 km/h (when reversing < 20 km/h)
If all of the conditions for gear shifting are met, the transfer case control unit actuates the transfer case actuator motor. The change of transmission ratio from HIGH to LOW or LOW to HIGH takes place in the transfer case.
All of the models in the new G-Class feature permanent all-wheel drive. The permanent all-wheel drive system operates with a 2-speed transfer case with reduction gear that is directly flange-mounted to the 7-speed planetary automatic transmission or 5-speed automatic transmission (G 55 AMG).
During normal driving, 2 card an shafts with universal joints transmit the drive torque equally to the front and rear axle. A bevel gear differential balances the rotational speeds.
The torque is distributed between the front and rear axles of the permanent four-wheel drive in the ratio 50:50.
The electronic vehicle dynamics control system ESP/4ETS is used to improve traction control and vehicle dynamics control in both on-road and off-road driving.
· 1 Cardan shaft
· 2 Transfer case
· 3 Front differential
· 4 Transmission
· 5 Rear differential
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