7G-Tronic is Mercedes-Benz's trademark name for its seven-speed automatic transmission, starting off with the W7A 700 and W7A 400 (Wandler-7-Gang-Automatik bis 700 oder 400 Nm Eingangsdrehmoment; converter-7-gear-automatic with 516 or 295 ft·lb maximum input torque; type 722.9) as core models.
Abstract
This fifth-generation transmission was the first seven-speed automatic transmission ever used on a production passenger vehicle.[1] In all applications this transmission is identified as the New Automatic Gearbox Generation Two, or NAG2. It initially debuted in Autumn 2003 on five different eight-cylinder models: the E500, S 430, S 500, CL 500, and SL 500. It also soon became available on many six-cylinder models. Turbocharged V12 engines, four cylinder applications and commercial vehicles continued to use the older Mercedes-Benz 5G-Tronic transmission for many years.
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.[1] It has two reverse gear ratios.
The transmission can skip gears when downshifting. It also has a torque converter lock-up on all seven 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.[citation needed] The 7G-Tronic transmission is built at the Mercedes-Benz Stuttgart-Untertuerkheim plant in Germany, the site of Daimler-Benz's original production facility.
Progress is reflected in 7 forward gears[a] using 11 main components,[3][4][5] compared to 5 forward gears[b] with 9 main components in the previous 5G-Tronic transmission. This turns out the design as advanced compared to its predecessor but less economical compared to its competitors. It uses no bands nor sprag clutches.[4] It is fully electronic controlled. Torque converter lock-up can operate in all 7 forward gears.[4]
^Layout • Input and output are on opposite sides • Planetary gearset 2 (the outer Ravigneaux gearset) is on the input (turbine) side • Input shafts are R1 and, if actuated, R3 • Output shaft is C3 (planetary gear carrier of gearset 3)
^Sun 1: sun gear of gearset 1: inner Ravigneaux gearset
^Ring 1: ring gear of gearset 1: inner Ravigneaux gearset
^Sun 2: sun gear of gearset 2: outer Ravigneaux gearset
^Ring 2: ring gear of gearset 2: outer Ravigneaux gearset
^ abcdStandard 50/50: 50/50 are above/below average step With consistently falling gear steps (row highlighted in yellow), the lower half of them (rounded down, here the first three) is always larger and the upper half of them (rounded up, here the last three) is always smaller than the average gear step (cell highlighted in yellow two rows above). Deviating gear steps (red bold) indicate an unfavorable gearset selection
^ abcdeIn line with the logic for the 2nd reverse gear of the predecessor 5G-Tronic, the extended layout provides this 3rd reverse gear, but it was not used in the transmission that was finally launched on the market
^ abcStandard REV: reverse gear is similar to 1st gear Reverse and 1st gear should have the same ratio. Plus 11 % minus 10 % compared to 1st gear is good, plus 25 % minus 20 % is acceptable (red); even larger deviations (bold) can impair the driving experience, especially when towing a trailer. A torque converter can only partially compensate for this deficiency
^Standard FIRST: gear step 1st to 2nd gear With consistently falling gear steps, the largest gear step is the one from the 1st to the 2nd gear, although it should be limited for a smooth gear shift. A ratio step of up to 5 : 3 (1.6667 : 1) is good, up to 7 : 4 (1.7500 : 1) is acceptable (red); above (bold) is unsatisfactory
^ abcdStandard SECOND: 2nd degree steps above 1 With consistently rising (from right to left) gear steps, each 2nd degree step (first row highlighted in green) is larger than 1. Smaller than its predecessor is acceptable (red); smaller than 1 (bold) is unsatisfactory
^ abcdStandard SPEED: shaft speed difference increase One difference that runs counter to the consistent increase in shaft speed differences (second row highlighted in green) is acceptable (red); two consecutive ones (bold) indicate an unfavorable gearset selection
^C1 and C2 (the common Ravigneaux carrier 1 + 2), and R4 share a common shaft R3 and C4 (carrier 4) share a common shaft
^Blocks S1 (sun gear of the inner Ravigneaux geaset)
In normal condition it sequentially shift gears, but if required it can skip some gears, that are: 7 to 5, 6 to 2, 5 to 3 and 3 to 1.[4]
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.[6]
„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.[4]
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.[7]
In 2007, 7G-Tronic transmission with AMG SPEEDSHIFT was also called '7G-Tronic Sport'.[8]
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.[9]
The MCT is fitted with four drive modes: "C" (Comfort), "S" (Sport), "S+" (Sport plus) and "M" (Manual) and boasts 100 millisecond 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 AMG CLS 63 and E 63 models, as well as their "S--Model" variants. Improved with the release of the 2015 model year, by decreasing the lag time between shifts.
Applications
Mercedes models
Mercedes C-Class
2005-2007 Mercedes-Benz W203 (C 320 CDI, C 230, C 280, C 350; post-facelift)