Mercedes 7G-Tronic Plus

Transmission Evolution
Torque Converter
Damper Development
Fuel Economy
Summary
 

To view much more technical information about the Mercedes 7G-Tronic Plus click on our PDF file below.

Mercedes 7G-Tronic Plus PDF file

Mercedes 7G Tronic Plus

In 2010, Mercedes-Benz launched the latest version of its seven-speed automatic transmission 7G-Tronic called 7G-Tronic Plus for passenger cars in the S-Class, R-Class and E-Class with the V6 diesel engine and in the CL-Class with the new V8 gasoline engine. The S-Class will also be offered with the four-cylinder inline diesel engine and with the new V6 and V8 gasoline engines from the start of 2011 with this new transmission.

The new, sixth generation automatic transmission 7G-Tronic Plus is internally designated the W7C700 and W7X700 (for the integrated all-wheel-drive version 4Matic and W7C1000 for the reinforced transmission version).

Torque Converter

A modular, next-generation torque converter was designed with an improved hydraulic circuit, torque converter lock-up clutch, and dampers to accommodate, in particular, the dramatic increase in torque generated by the new V8 gasoline engine and the torque increase of the four and six-cylinder diesel engines.

The torque converter assumes many functions in modern automatic transmissions. When the vehicle accelerates from a stop, for example, the engine must be smoothly connected to the drive line and output efficiently transferred to ensure high performance.

Torsinal De-Coupling

Damper development was mainly influenced by three factors with respect to the torque converter, all of which target a reduction in CO2 emissions.

  • Increasing Output & Torque with ever-smaller engines.
  • Good power delivery of the engines at low speed, in conjunction with today's typically wide gearbox ratio, makes it possible to introduce an exceptionally low-speed drive program.
  • Developers wanted to eliminate slippage of the torque converter lock-up clutch in order to promote efficient power delivery.

The answer to these three challanges came in the form of a centrifugal pendulum damper, designed in conjunction with the company LuK.

Fuel Economy

The average percentage fuel economy improvement by the improved transmission is shown in the diagram above, with 7% in total. Using start-stop a further 4% is possible.

Summary

The new seven-speed automatic transmission from Daimler is equipped with a start-stop system for the first time, made possible with the addition of an electric auxiliary transmission oil pump that safeguards the pressure supply when the constant-flow pump is not running (engine off). The vehicle can start off again without delay following a brief stop.

A next-generation torque converter optimizes NVH levels thanks to more advanced dampers, which also noticeably reduce fuel consumption. This is achieved by greatly reducing the slip of the lock-up clutch (actively regulated zero slip) in conjunction with better mechanical damper insulation from very low engine speeds and during gear shifts, despite the fact that the nominal and reaction torque of the engines has increased.

Consumption-reducing measures were implemented for the transmission as well and include new automatic transmission fluid (ATF134FE) with reduced viscosity in conjunction with an optimized additives package, redesigned internal componentry for the transmission, with new materials, bearings, disk linings, and geometric enhancements, adapted software, lower service pressure at many operating points, and better internal seals.

The reworked electronic control unit for the transmission, together with improved software, make shifting smoother.