G-Tronic transmission: essential information, types, features & technical parameters

G-Tronic transmission: essential information, types, features & technical parameters

G-Tronic is a series of automatic transmissions with a manual mode, installed on Mercedes-Benz and SsangYong cars. The first G-Tronic was a 4-speed automatic gearbox released in 1981. Nowadays, the manufacturer produces a 9-speed G-Tronic transmission. All these gearboxes are proprietary developments of Daimler AG. They are characterised by reliability, high performance, and can transmit high torques.

 G-Tronic operating principle 

G-Tronic is based on a classic automatic transmission with hydraulic torque converter and electronic control. Starting from the 90s, it features a torque converter lockup. Initially, this allowed a driver to select the uppermost gear (one or several higher gears could be locked out).  Later it helped to implement a full manual mode featured on all the following generations of this automatic transmission.

As a rule, these transmissions have several automatic modes of operation, for instance, Sport, Comfort, Eco. The driver can select the desired mode using a button, special switch, or selector on the central console. To switch to manual mode, you have to put the gear selector in the “D” position and then nudge it left, towards the “–” sign. This locks up the gear engaged at the moment. After this, you can shift the gears up or down by nudging the selector towards “+” or “–”, respectively. Manual shifting can be performed with the help of paddle shifters as well (if the vehicle has them).

Popular G-Tronic transmissions

Version Gearbox code Number of gears Max engine capacity, L Max engine torque, N⋅m Production start Car layout Mercedes-Benz models SsangYong models
4G-Tronic 722.3 (W4A040) 4 6.0 570 1981 RWD S-Class W126; E-Class W123; S-Class  W140; SL R107; E-Class W124; SL R129
4G-Tronic 722.4 (W4A020) 4 3.0 250 1981 RWD S-Class W126; E-Class W123; C-Class W202; E-Class W124
5G-Tronic 722.6 (W5A330, W5J400, W5A580) 5 3.5; 4.3; 6.0 350; 420; 580 1996 RWD, AWD C-Class W202; S-Class W221; C-Class W204; E-Class W211; C-Class W203; E-Class W212; M-Class W163; S-Class W140; S-Class W220 Rodius AJ; Rexton Y200
5G-Tronic 722.7 (W5A180) 5 1.9 205 1998 FWD Vaneo W414; A-Class W168
7G-Tronic 722.9 (W7X550, W7A700, W7B700, ) 7 3.5; 5.5; 6.3 550; 700; 850 2003 RWD, AWD C-Class W204; S-Class W221; E-Class W211; S-Class W220; M-Class W164; C-Class W205; E-Class W212; M-Class W166 Chairman W
9G-Tronic 725.0 (NAG3) 9 6.7 1000 2013 RWD, AWD C-Class W205; GLE W166; S-Class W222; E-Class W213; GLS X166; CLS W218  

Common malfunctions of G-Tronic transmissions

Malfunctions Transmissions
A clogged gearbox oil cooler causes the transmission to overheat. 722.4 (W4A020); 722.3 (W4A040)
A spring of the reverse gear clutch pack breaks down. 722.3 (W4A040); 722.4 (W4A020)
The vacuum modulator valve breaks down often. 722.4 (W4A020); 722.3 (W4A040)
A bushing between the transmission shafts is of insufficient strength and breaks down often. 722.6 (W5A330, W5J400, W5A580)
Solenoids of the valve body get clogged with wear products of the clutch packs. 722.6 (W5A330, W5J400, W5A580)
Torque converter lockup solenoid stops working prematurely. 722.6 (W5A330, W5J400, W5A580)
A circuit board of the valve body often fails. 722.7 (W5A180); 722.9 (W7A700, W7X550, W7B700)
One of the clutch drums gets damaged. 722.7 (W5A180)
Vibrations caused by aggressive driving behaviour lead to severe damage to the transmission housing. 722.9 (W7B7000, W7X550, W7A70)
Transmission malfunctions caused by soiling and failure to replace the transmission fluid in due time. 725.0 (NAG3)

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