Automatic Transmission (AT), Function - GF27.10-P-0001ANI

Transmission 725.0 in model 253 

Courtesy of MERCEDES-BENZ USA

Automatic transmission (AT), general 

The automatic transmission 9G-TRONIC 725.0 is a completely new electronically regulated automatic transmission with 9 forward gears and one reverse gear. The gear ratios for the gear ranges are achieved by planetary gear sets. All the transmission functions and components for this automatic transmission are combined in one assembly module.

The fully integrated transmission control controller unit (Y3/8) located in the automatic transmission minimizes the number of interfaces to the wiring harness in the vehicle.

Use of the new fully integrated transmission control (VGS) bring with it the following additional advantages:

• High electromagnetic compatibility (prevention of interaction between multiple electronic components)
• Fast current control as well as the compensation of on-board electrical system fluctuations, which leads to increased shift quality.
• Accurate determination of measurements relevant to shift operations and faster evaluation of the measured values

Increased service life, reduced fuel consumption and maximum gearshift comfort can be achieved with the following:

• A new transmission design with 9 speeds and a gear ratio spread of 9.156 (transmission 725.004/011/041/044/054) or of 8.91 (transmission 725.008/048/058/096)
• New, optimized transmission components
• Reduction of working pressure
• Implementation of a completely new software with additional comfort and dynamic functions
• New actuation system concept with two oil pumps (primary pump and electrical auxiliary oil pump)

The automatic transmission can be subdivided into the following assemblies:

• Torque converter with torsional damper, centrifugal pendulum and torque converter lockup clutch (except transmission 725.096)
• Wet clutch with 2-stage torsional damper (transmission 725.096)
• New oil pump (primary pump) in off-axis version for generating the necessary oil pressure and for reliable lubrication of the shift elements and bearing points
• Electrical auxiliary oil pump for generating required oil pressure, for guaranteeing lubrication of shift elements and bearing points at engine OFF and for supporting the primary pump
• Transmission housing with mechanical transmission components (planetary gear sets, electrohydraulically operated park pawl, multidisk clutches and multidisk brakes)
• Fully integrated transmission control controller unit with integrated fully integrated transmission control unit

Two-mass flywheel

The two-mass flywheel is used to reduce torsional vibrations. This contains 2 centrifugal pendulums. This serves to significantly reduce the torsional vibrations, even at cylinder deactivation.

Transmission 725.0 in model 253

with code 460 (Canada version)

Transmission 725.0 in model 253

with code 494 (US version)

Transmission 725.0 in model 253

with code 830 (Vehicles for China, additional parts)

Remote start 

When gear range "P" is engaged, the driver can use his mobile phone to contact the service provider to then execute the "Remote Start" function. The vehicle then starts the combustion engine for a limited period of time to permit pre-entry climate control.

Further subfunctions are described in separate documents: 

• Key-P function 
• Emergency-P function 
• Parking interlock controller, function 
• Power flow with forward travel function 
• Power flow with reverse travel function 
• Transmission oil cooling with transmission oil heat exchanger, function 
• A/T oil supply, function 
• Shift operation, function 
• Transmission control, function 
• Engage gear range, function 
• Limp-home mode, function 
• Torque converter lockup clutch control pressure function (except transmission 725.096) 
• Torque converter lockup clutch control function (except transmission 725.096) 
• Working/lubrication/shift pressure, function 
• Wet clutch function (transmission 725.096) 
• Wet clutch control pressure function (transmission 725.096)