Mercedes-Benz 7G-Tronic transmission

7G-Tronic is Mercedes-Benz's trademark name for its 7-speed automatic transmission type 722.9. It was produced from 2003 to 2020 in different variants as converter-7-gear-automatic transmission (). The core models W7A 400 and W7A 700 are for engines up to or maximum input torque.

Key data

+ Gear ratios Model Type FirstDeliv-ery Gear Total Span Avg.Step Components Nomenclature R 2 R 1 1 2 3 4 5 6 7 Nomi-nal Effec-tive Cen-ter Total perGear Cou-pling GearsCount Ver-sion Maximum Input Torque W7A 400W7A 700W7A 900 722.9NAG 2 2003 4 Gearsets4 Brakes3 Clutches W 7 A

History

This fifth-generation transmission was the first 7-speed automatic transmission ever used on a production passenger vehicle. It initially was introduced in autumn 2003 on five different V8-cylinder models: the E 500, S 430, S 500, CL 500, and SL 500. It became available on many 6-cylinder models too. Turbocharged V12 engines, 4-cylinder applications and commercial vehicles continued to use the older Mercedes-Benz 5G-Tronic transmission for many years.

Development took place at the group's headquarters in Stuttgart-Untertuerkheim. The transmission was produced only at the Daimler plant not far away in Stuttgart-Hedelfingen, the site of Daimler-Benz's original production facility. In July 2009, Mercedes-Benz announced they were working on a new nine-speed automatic.

Specifications

Operating modes

Regular

The W7A uses neither bands nor sprag clutches. It is fully electronic controlled. On vehicles with 6 or 8 cylinder engines with comfort mode engaged, as well as on off-road vehicles with low range selected, the transmission will always use 2nd gear as initial gear.

The transmission can skip gears when downshifting. It also has a torque converter lock-up on all 7 gears, allowing better transmission of torque for improved acceleration. The transmission's casing is made of magnesium alloy, a first for the industry, to save weight.

„Limp-home mode“

If the transmission control unit senses a critical fault during driving, it will activate an emergency operating mode: Upon hydraulic failures, it will stop shifting gears and permanently retain the currently selected gear; if the failure can be pinpointed to one of the internal hydraulic control valves, the transmission will continue shifting but stop using the affected gear(s). Upon electrical failure, the transmission shifts to 6th gear. If the critical fault persists after the vehicle is stopped and the engine restarted, only 2nd gear and reverse gear #2 are available.

AMG SpeedShift

AMG SpeedShift TCT

The TCT transmission is essentially the 7G-Tronic automatic transmission including "Torque Converter Technology". Sporty, performance-oriented version with the same gear ratios. First used in 2005 Mercedes-Benz SLK 55 AMG. In 2007, 7G-Tronic transmission with AMG SpeedShift was also called '7G-Tronic Sport'.

AMG SpeedShift MCT

Mercedes-AMG developed the 7-speed MCT "Multi Clutch Technology" planetary automatic transmission. The MCT transmission is essentially the 7G-Tronic automatic transmission without a torque converter. Instead of a torque converter, it uses a compact wet startup clutch to launch the car from a stop and also supports computer-controlled double-clutching. The MCT (Multi-Clutch Technology) acronym refers to a planetary (automatic) transmission's multiple clutches and bands for each gear.

The MCT is fitted with 4 drive modes: "C" (Comfort), "S" (Sport), "S+" (Sport plus) and "M" (Manual) and boasts 0.1 second shifts in "M" and "S+" modes. MCT-equipped cars are also fitted with the new AMG Drive Unit with an innovative Race Start function. The AMG Drive Unit is the central control unit for the AMG SpeedShift MCT 7-speed sports transmission and all driving dynamics functions. The driver can change gears either using the selector lever or by nudging the steering-wheel shift paddles. The new Race start Function is a launch control system that enables the driver to call on maximum acceleration while ensuring optimum traction of the driven wheels.

It is available on the 2009 SL 63 AMG and E 63 AMG, and will be used for the 2011 S 63 AMG and CL 63 AMG, and the 2012 CLS 63 AMG and C 63 AMG. Compulsory on the 2014 CLS 63 and E 63 AMG models, as well as their "S--Model" variants. Improved with the release of the 2015 model year, by decreasing the lag time between shifts.

Planetary gearset concept

Improved fuel economy

The main objective in replacing the predecessor model was to improve vehicle fuel economy with extra speeds and a wider gear span to allow the engine speed level to be lowered (downspeeding), which is a decisive factor in improving energy efficiency and thus reducing fuel consumption. In addition, the lower engine speed level improves the noise-vibration-harshness comfort and the exterior noise is reduced.

Torque converter lock-up can operate in all 7 forward gears. The company claims that the 7G-Tronic is more fuel efficient and has shorter acceleration times and quicker intermediate sprints than the outgoing 5-speed automatic transmission.

Reduced manufacturing complexity

In order to avoid a further increase in manufacturing complexity while expanding the number of gear ratios, Mercedes-Benz switched from the conventional design method—in which the planetary gearset concept was limited to a purely serial or in-line power flow—to a more modern design method that utilizes a planetary gearset concept with combined parallel and serial power flow. This was only possible thanks to computer-aided design and has resulted in a globally patented gearset concept. The resulting progress is reflected in a better ratio of the number of gears to the number of components used compared to existing layouts.

This is Mercedes-Benz second generation of advanced automatic transmissions. The design is more advanced than its direct predecessor, but significantly less economical than its competitors. Since Mercedes can charge higher prices than many of its competitors, it was possible to include the 7G-Tronic in the range. With its all new parallel power flow the W7A is referred to at Mercedes-Benz as NAG 2 (New Automatic Gearbox Generation, starting with type 722.6 as generation 1 and continuing with type 722.9 as generation 2).

+ Planetary gearset concept: manufacturing complexity WithAssessment Output:GearRatios InnovationElasticityΔ Output : Δ Input Input: Main Components Total Gearsets Brakes Clutches W7ARef. Object Topic Δ Number Relative Δ Δ Output Δ Input W7AW5A 75 Progress 119 43 43 33 Δ Number 2 2 1 1 0 Relative Δ W7AZF 8HP 78 LateMarket Position 119 44 43 32 Δ Number -1 -2 0 -1 -1 Relative Δ W7AZF 6HP 76 EarlyMarket Position 118 43 42 33 Δ Number 1 3 1 2 0 Relative Δ W7A3-Speed 73 HistoricalMarket Position 117 42 43 32 Δ Number 4 4 2 1 1 Relative Δ

Quality

The biggest weakness of the gearset concept is the two consecutive reductions in speed increase in 6th and 7th gear.

The layout brings the ability to shift in a non-sequential manner – if required it can skip some gears, that are: 7 to 5, 6 to 2, 5 to 3 and 3 to 1.

It has 2 reverse gears.

+ Planetary gearset concept: gear ratio quality In-Depth AnalysisWith AssessmentAnd Torque RatioAnd Efficiency Calculation Planetary Gear Set: Teeth Count Nomi-nalEffec-tive Cen-ter Ravigneaux Simple Avg. ModelType VersionFirst Delivery S1R1 S2R2 S3R3 S4R4 BrakesClutches GearRatioSpan GearStep Gear R 2 R 1 1 2 3 4 5 6 7 GearRatio Step Δ Step ShaftSpeed Δ ShaftSpeed TorqueRatio Efficiency W7A 400W7A 700W7A 900722.9 NAG 2 · 2003 4286 86110 2876 46114 43 Gear R 2 R 1 1 2 3 4 5 6 7 GearRatio Step 1.5313 1.0000 1.4884 1.2189 1.1276 Δ Step 1.0605 1.1226 1.0810 Speed –1.9622 1.0000 1.5313 2.2791 3.1987 4.3772 Δ Speed 0.6808 1.0000 0.5313 0.7478 0.9196 1.1785 TorqueRatio –2.1400–2.0955 –3.2433–3.1594 4.25604.1965 2.80832.7833 1.89931.8886 1.36111.3574 1.0000 0.81310.8094 0.71790.7130 Efficiency 0.95930.9394 0.94950.9250 0.97230.9587 0.98240.9737 0.98890.9834 0.99460.9919 1.0000 0.99120.9866 0.98680.9799 Actuated shift elements Brake 1 ❶ ❶ ❶ Brake 2 ❶ ❶ ❶ ❶ Brake 3 ❶ ❶ ❶ Brake BR ❶ ❶ Clutch 1 ❶ ❶ ❶ Clutch 2 ❶ ❶ ❶ ❶ Clutch 3 ❶ ❶ ❶ ❶ ❶ ❶ ❶ ❶ Geometric ratios: speed conversion GearRatioR2 & 5OrdinaryElementaryNoted GearRatioR1 & 1OrdinaryElementaryNoted GearRatio2–4OrdinaryElementaryNoted GearRatio6 & 7OrdinaryElementaryNoted Kinetic ratios: torque conversion TorqueRatioR2 & 5 TorqueRatioR1 & 1 ! TorqueRatio2–4 ! TorqueRatio6 & 7

Applications

+ Variants and applications Model Car Model Mercedes models C-Class 2005–2007 W 203 (C 320 CDI, C 230, C 280, C 350; post-facelift) 2005–2007 CL 203 (C 230 Sport Coupé, C 350 Sport Coupé; post-facelift), (CLC 250, CLC 350) 2007–2011 W 204 (C 320 CDI) 2011–2018 W 204 (C 63 AMG, C 63 AMG Black Series) 2014 W 205 (C 180) E-Class 2003–2009 W 211 (V6 & V8 models, RWD only) 2009–2016 W 212 (V6 & V8 models, RWD only) S-Class 2013–2017 W 222 (all models except Maybach S 500 and Maybach S 500 4Matic) 2017–2020 W 222 (V12 models only) SLK-Class 2004–2011 R 171 2011–2015 R 172 CLS-Class 2003–2010 C 219 2010–2018 C 218 CLK-Class 2002–2010 C 209 CLA-Class 2016–2019 C 117 Non Mercedes-Benz models Infiniti 2014–2019 Q50 (2.0t (M274 DE20 LA)) 2015–2016 Q50 (2.2d (OM651 22 LA)). 2017–2018 Q60 (2.0t (M274 DE20 LA)) SsangYong Motor 2017–2020 Rexton G4 (2.2 e-XDi Euro 6 Turbo-Diesel) Rodius Korando Turismo (in South Korea) Rodius Turismo (in UK)

Mercedes-Benz 7G-Tronic transmission

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