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

<div style="overflow:auto">

{|class="wikitable collapsible" style="text-align:center"

|+ Gear&nbsp;ratios

!rowspan="2"| Model

!rowspan="2"| Type

!rowspan="2"| First<br />Deliv-<br />ery

!colspan="9"| Gear

!colspan="3"| Total Span

!rowspan="2"| Avg.<br />Step

!colspan="2"| Components

!colspan="4"| Nomenclature

|-

! R&nbsp;2

! R&nbsp;1

! 1

! 2

! 3

! 4

! 5

! 6

! 7

! Nomi-<br />nal

! Effec-<br />tive

! Cen-<br />ter

! Total

! per<br />Gear

! Cou-<br />pling

! Gears<br />Count

! Ver-<br />sion

! Maximum&nbsp;Input&nbsp;Torque

|-

|colspan="22" style="background:#AAF"|

|-

! W7A&nbsp;400<br />W7A&nbsp;700<br />W7A&nbsp;900

| 722.9<br />NAG&nbsp;2<br />

| 2003

|

|

|

|

|

|

|

|

|

|

|

|

|

| 4&nbsp; Gearsets<br />4 Brakes<br />3 Clutches

|

| W

| 7

| A

| <br /><br />

|-

|colspan="22" style="background:#AAF"|

|-

|colspan="22"|

|-

|colspan="22" style="background:#AAF"|

|}

</div>

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&nbsp;500, S&nbsp;430, S&nbsp;500, CL&nbsp;500, and SL&nbsp;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.

Specifications

Operating modes

Regular

The W7A uses neither bands nor sprag clutches.

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. 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&nbsp;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&nbsp;63 AMG and E&nbsp;63 AMG, and will be used for the 2011 S&nbsp;63 AMG and CL&nbsp;63 AMG, and the 2012 CLS&nbsp;63 AMG and C&nbsp;63 AMG. Compulsory on the 2014 CLS&nbsp;63 and E&nbsp;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.<br />9

| 4<br />3

| 4<br />3

| 3<br />3

|-

! Δ Number

| 2

| 2

| 1

| 1

| 0

|-

! Relative Δ

| <br /><math>\tfrac{2} {5}</math>

| <br /><math>\tfrac{2} {5} : \tfrac{2} {9}= \tfrac{2} {5} \cdot \tfrac{9} {2}= \tfrac{9} {5}</math>

| <br /><math>\tfrac{2} {9}</math>

| <br /><math>\tfrac{1} {3}</math>

| <br /><math>\tfrac{1} {3}</math>

| <br /><math>\tfrac{0} {3}</math>

|-

!colspan="7"|

|-

! W7A<br />ZF 8HP

| 7<br />8

!rowspan="2"| Late<br />Market Position

| 11<br />9

| 4<br />4

| 4<br />3

| 3<br />2

|-

! Δ Number

| -1

| -2

| 0

| -1

| -1

|-

! Relative Δ

| <br /><math>\tfrac{-1} {8}</math>

|

| <br /><math>\tfrac{2} {9}</math>

| <br /><math>\tfrac{0} {4}</math>

| <br /><math>\tfrac{1} {3}</math>

| <br /><math>\tfrac{1} {2}</math>

|-

!colspan="7"|

|-

! W7A<br />ZF 6HP

| 7<br />6

!rowspan="2"| Early<br />Market Position

| 11<br />8

| 4<br />3

| 4<br />2

| 3<br />3

|-

! Δ Number

| 1

| 3

| 1

| 2

| 0

|-

! Relative Δ

| <br /><math>\tfrac{1} {6}</math>

|

| <br /><math>\tfrac{3} {8}</math>

| <br /><math>\tfrac{1} {3}</math>

| <br /><math>\tfrac{2} {2}</math>

| <br /><math>\tfrac{0} {3}</math>

|-

!colspan="7"|

|-

! W7A<br />3-Speed

| 7<br />3

!rowspan="2"| Historical<br />Market Position

| 11<br />7

| 4<br />2

| 4<br />3

| 3<br />2

|-

! Δ Number

| 4

| 4

| 2

| 1

| 1

|-

! Relative Δ

| <br /><math>\tfrac{4} {3}</math>

| <br /><math>\tfrac{4} {3}: \tfrac{4} {7}= \tfrac{4} {3} \cdot \tfrac{7} {4}= \tfrac{7} {3}</math>

| <br /><math>\tfrac{4} {7}</math>

| <br /><math>\tfrac{2} {2}</math>

| <br /><math>\tfrac{1} {3}</math>

| <br /><math>\tfrac{1} {2}</math>

|-

|colspan="7" style="background:#AAF"|

|-

|colspan="7"|

|-

|colspan="7" style="background:#AAF"|

|}

</div>

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. <!-- Is this true? My 2014 E350cdi does not start in 2nd also using Comfort mode. Answer: Absulutely sure. 2014 E350 cdi is equipped with the 9G-Tronic: introduced September 2013 in the E 350 cdi. The 9G-Tronic has only one reverse gear. Cheers Musikgeniesser-->

<div style="overflow:auto">

{|class="wikitable collapsible" style="text-align:center"

|+ Planetary&nbsp;gearset&nbsp;concept: gear&nbsp;ratio&nbsp;quality

!rowspan="2" colspan="4"| In-Depth Analysis {\omega_{1;n} = \frac{\omega_{1;n {\omega_{2;n = \frac{\omega_t} {\omega_{2;n</math><br />With Assessment<br />And Torque Ratio {\omega_{2;n = \frac{T_{2;n} \eta_{n;\eta_0 {T_{1;n</math>

• whereby <math>\eta_{n;\eta_0}</math> may vary from gear to gear according to the formulas listed in this table and <math>0 \le \eta_{n;\eta_0} \le 1</math><br />And Efficiency Calculation

!colspan="4"| Planetary Gear Set: Teeth

!rowspan="2"| Count

!rowspan="2"| Nomi-<br />nal {\omega_{2;1 = \frac{\frac{\omega_{2;n {\omega_{2;1} \omega_{2;n} {\frac{\omega_{2;1 {\omega_{2;1} \omega_{2;n} = \frac{\frac{1} {\omega_{2;1} {\frac{1} {\omega_{2;n} = \frac{\frac{\omega_t} {\omega_{2;1} {\frac{\omega_t} {\omega_{2;n} = \frac{i_1} {i_n}</math>

• A wider span enables the
• downspeeding when driving outside the city limits
• increase the climbing ability
• when driving over mountain passes or off-road
• or when towing a trailer<br />Effec-<br />tive {max(\omega_{2;1};|\omega_{2;R}|)} = \frac{min(i_1;|i_R|)} {i_n}</math>
• The span is only effective to the extent that
• the reverse gear ratio
• matches that of 1st gear
• see also Standard R:1

Digression<br />Reverse gear

• is usually longer than 1st gear
• the effective span is therefore of central importance for describing the suitability of a transmission
• because in these cases, the nominal spread conveys a misleading picture
• which is only unproblematic for vehicles with high specific power

Market participants

• Manufacturers naturally have no interest in specifying the effective span
• Users have not yet formulated the practical benefits that the effective span has for them
• The effective span has not yet played a role in research and teaching

Contrary to its significance

• the effective span has therefore not yet been able to establish itself
• either in theory
• or in practice. <br />

End of digression

! Cen-<br >ter

|-

!colspan="2"| Ravigneaux

!colspan="2"| Simple

! Avg. {\omega_{2;1 \right) ^\frac{1} {n-1} = \left( \frac{i_1} {i_n} \right) ^\frac{1} {n-1}</math>

• There are <math>n-1</math> gear steps between <math>n</math> gears
• with decreasing step width
• the gears connect better to each other
• shifting comfort increases

|-

|colspan="11" style="background:#AAF"|

|-

! Model<br />Type

!colspan="3"| Version<br />First Delivery

! S₁<br />R₁

! S₂<br />R₂

! S₃<br />R₃

! S₄<br />R₄

! Brakes<br />Clutches

! Gear<br />Ratio<br />Span

! Gear<br />Step

|-

! Gear

!

! R 2

! R 1

! 1

! 2

! 3

! 4

! 5

! 6

! 7

|-

! Gear<br />Ratio

! <math>\color{grey} {i_{R3</math>

! <math>{i_{R2</math>

! <math>{i_R}</math>

! <math>{i_1}</math>

! <math>{i_2}</math>

! <math>{i_3}</math>

! <math>{i_4}</math>

! <math>{i_5}</math>

! <math>{i_6}</math>

! <math>{i_7}</math>

|-

! Step

! <math>\color{grey} \frac{i_{R2 {i_{R3</math>

! <math>\frac{i_{R1 {i_{R2</math>

! <math>-\frac{i_{R1 {i_1}</math>

! <math>\frac{i_1} {i_1}</math>

! <math>\frac{i_1} {i_2}</math>

! <math>\frac{i_2} {i_3}</math>

! <math>\frac{i_3} {i_4}</math>

! <math>\frac{i_4} {i_5}</math>

! <math>\frac{i_5} {i_6}</math>

! <math>\frac{i_6} {i_7}</math>

|-

! Δ&nbsp;Step

!style="background:#DDF"|

! <math>\color{grey}\tfrac{i_{R1 {i_{R2 : \tfrac{i_{R2 {i_{R3</math>

! style="background:#DDF"|

! style="background:#DDF"|

! <math>\tfrac{i_1} {i_2} : \tfrac{i_2} {i_3}</math>

! <math>\tfrac{i_2} {i_3} : \tfrac{i_3} {i_4}</math>

! <math>\tfrac{i_3} {i_4} : \tfrac{i_4} {i_5}</math>

! <math>\tfrac{i_4} {i_5} : \tfrac{i_5} {i_6}</math>

! <math>\tfrac{i_5} {i_6} : \tfrac{i_6} {i_7}</math>

! style="background:#DDF"|

|-

! Shaft<br />Speed

! <math>\color{grey}\frac{i_1}{i_{R3</math>

! <math>\frac{i_1} {i_{R2</math>

! <math>\frac{i_1} {i_{R1</math>

! <math>\frac{i_1} {i_1}</math>

! <math>\frac{i_1} {i_2}</math>

! <math>\frac{i_1} {i_3}</math>

! <math>\frac{i_1} {i_4}</math>

! <math>\frac{i_1} {i_5}</math>

! <math>\frac{i_1} {i_6}</math>

! <math>\frac{i_1} {i_7}</math>

|-

! Δ Shaft<br />Speed

! <math>\color{grey}\tfrac{i_1} {i_{R2 - \tfrac{i_1}{i_{R3</math>

! <math>\tfrac{i_1} {i_{R1 - \tfrac{i_1} {i_{R2</math>

! <math>0 - \tfrac{i_1} {i_{R1</math>

! <math>\tfrac{i_1} {i_1} - 0</math>

! <math>\tfrac{i_1} {i_2} - \tfrac{i_1} {i_1}</math>

! <math>\tfrac{i_1} {i_3} - \tfrac{i_1} {i_2}</math>

! <math>\tfrac{i_1} {i_4} - \tfrac{i_1} {i_3}</math>

! <math>\tfrac{i_1} {i_5} - \tfrac{i_1} {i_4}</math>

! <math>\tfrac{i_1} {i_6} - \tfrac{i_1} {i_5}</math>

! <math>\tfrac{i_1} {i_7} - \tfrac{i_1} {i_6}</math>

|-

! Torque<br />Ratio

! <math>\color{grey}\mu_{R3}</math>

! <math>\mu_{R2}</math>

! <math>\mu_{R1}</math>

! <math>\mu_1</math>

! <math>\mu_2</math>

! <math>\mu_3</math>

! <math>\mu_4</math>

! <math>\mu_5</math>

! <math>\mu_6</math>

! <math>\mu_7</math>

|-

! Efficiency<br /><math>\eta_n</math>

! <math>\color{grey}\frac{\mu_{R2 {i_{R2</math>

! <math>\frac{\mu_{R2 {i_{R2</math>

! <math>\frac{\mu_{R1 {i_{R1</math>

! <math>\frac{\mu_1} {i_1}</math>

! <math>\frac{\mu_2} {i_2}</math>

! <math>\frac{\mu_3} {i_3}</math>

! <math>\frac{\mu_4} {i_4}</math>

! <math>\frac{\mu_5} {i_5}</math>

! <math>\frac{\mu_6} {i_6}</math>

! <math>\frac{\mu_7} {i_7}</math>

|-

|colspan="11" style="background:#AAF"|

|-

!rowspan="2"| W7A&nbsp;400<br />W7A&nbsp;700<br />W7A&nbsp;900<br />722.9

|rowspan="2" colspan="3"| <br /><br /><br />NAG&nbsp;2&nbsp;·&nbsp;2003)

• 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)

|-

|colspan="2" style="background:#AAF"|

|-

|colspan="2"|

|-

|colspan="2" style="background:#AAF"|

|}

</div>

See also

• List of Mercedes-Benz transmissions

References

External links

• 7g-Tronic ECU Repair
• GermanCarFans
• ATT24 GmbH