722.9 Technical Information

The Mercedes-Benz 722.9, marketed as 7G-TRONIC (internal name NAG2), is a seven-speed automatic transmission for longitudinal engines. Presented in 2003, it was the first seven-speed automatic in series production. It appeared first in the E 500 (W211), S 430 and S 500 (W220), CL 500 and SL 500, and by the end of the decade it had replaced the five-speed 722.6 in almost every model with a six- or eight-cylinder engine - from the C-Class to the G-Class. Later it spread to the four-cylinder models, the V-Class and the Sprinter. It was built in Stuttgart-Untertürkheim; from 2013 it gradually gave way to the nine-speed 9G-TRONIC (725.0), but stayed in certain models until 2020, and in the Sprinter until about 2022.

Its biggest novelty is also its most frequent problem: the control unit is not under the bonnet but on the conductor plate inside the oil pan, together with the speed sensors. In our experience the 722.9 is a robust transmission with a few well-known weak points: the conductor plate, the lock-up clutch of the torque converter and the fluid. Many of the "replace the gearbox" verdicts are premature. This page shows how to tell the versions apart, what the symptoms mean and which parts the repair needs.

Several different transmissions hide behind the number 722.9, and the first task in any repair is to establish which one is in front of you. The full designation is 722.9xx, where the last two digits identify the application; the model and serial number are recorded on the vehicle data card (Datenkarte, looked up by VIN) and on the plate on the housing. The units for four-cylinder engines (from 2008 in the GLK, widely from 2011) have a lower torque limit (W7A 400 in the catalogues), while those for V6 and V8 engines are W7A 700.

7G-TRONIC (2003 to June 2010). The first version runs on red fluid to specification MB 236.14, has a shallow steel pan with a flat filter and a control unit of the VGS1, VGS2 or VGS3 generation.

7G-TRONIC PLUS (from 21 June 2010). Identified by option code A89 on the data card and by transmission serial numbers from 2834527, but the changeover ran model by model into 2011 - the code and the serial number decide, not the model year of the car. It has a new torque converter with a centrifugal pendulum damper, blue MB 236.15 fluid, an electric auxiliary oil pump for the ECO start/stop function and a deeper pan with a triple filter. A quick check with the drain plug out: a green overflow tube on the PLUS, a white one on the early units. The two versions are not interchangeable - not the fluid, not the converter, not the conductor plate.

AMG. AMG SPEEDSHIFT 7G-TRONIC is the same transmission with a torque converter and AMG software (from the SLK 55 AMG in the R171; later ML 63, GL 63, G 63, S 65, SL 65). AMG SPEEDSHIFT MCT (722.93x, from the SL 63 AMG in 2008) uses the same gear train, but instead of a torque converter it has a wet start-up clutch, which is a wear part. On all AMG versions the current Mercedes specification is blue fluid (early AMG units before June 2010 left the factory on the red one), and the electrohydraulic unit is only replaced as a complete assembly.

4MATIC. On the C-, E-, S-, CLS-Class and GLK the transfer case is integrated into the rear of the transmission (NAG2i); on the ML, GL and R-Class it is a separate unit.

The 722.9 gradually became the standard automatic of Mercedes-Benz for rear-wheel drive and 4MATIC. Approximate years by model (only the versions with this transmission):

• S-Class and CL: W220 S 430 / S 500 (2003-2005); W221 all except V12 (2005-2013); W222 (2013-2017, V12 and Maybach to 2020); CL 500 (C215, 2003-2006); CL C216 except V12 (2006-2014)
• E-Class and CLS: W211 / S211 V6 and V8 rear-wheel drive, except E 55 AMG (2003-2009); W212 / S212 and C207 coupé (2009-2016, four-cylinder engines from 2011); CLS C219 (2004-2010); CLS C218 (2011-2017)
• C-Class, CLK, GLK and GLC: W203 V6 (2005-2007) and CLC; W204 (2007-2015, four-cylinder engines from 2011); W205 (2014-2017, hybrids to 2018); CLK C209 V6 and V8, except CLK 55 AMG (2005-2010); GLK X204 (2008-2015); GLC 350 e (2016-2019)
• SUVs and R-Class: ML W164 (2005-2011) and W166 (2011-2015); GLE W166 (the hybrid and some versions to 2018); GL X164 (2006-2012) and X166 (2012-2015); R W251 (2005-2013); G-Class W463 (2006-2018), except G 55 AMG
• Roadsters: SL R230 except V12 and SL 55 AMG (2003-2012) and R231 (2012-2016); SLK R171 (2004-2011) and R172 (2011-2016)
• Vans and pick-ups: V-Class and Vito W447 (2014-2019); Sprinter W906 with the four-cylinder diesel (2013-2018) and W907 in rear-wheel and all-wheel drive form (2018-2022); X-Class X 350 d (2018-2020)
• AMG: with torque converter - SLK 55 (R171 and R172), CLK 63, E 63 (W211), CLS 63 (C219), S 63 / CL 63 (M156), ML 63, R 63, GL 63, GLE 63 (W166), G 63 / G 65, S 65 (W222), SL 65 (R231); with MCT - SL 63 (R230 and R231), E 63 (W212), CLS 63 (C218), C 63 (W204 after 2011 and W205), S 63 / CL 63 (M157)
• Other makes: SsangYong Chairman W and Rexton G4; Infiniti Q50 2.2d and 2.0t with Mercedes engines

Common mix-ups: the Vito and Viano W639 only ever had the five-speed 722.6. The same goes for all four-cylinder W203, W211 and C209, all W211 4MATIC models and the Maybach 57/62. Chrysler, Jeep and Dodge never had this unit either - their NAG1 is the 722.6. The W213 E-Class is 9G-TRONIC only, and the A-, B-, CLA- and GLA-Class use the 7G-DCT dual-clutch gearbox.

The gear train is compact for seven speeds - one Ravigneaux planetary set and two simple ones, three multi-plate clutches (K1, K2, K3) and four brakes (B1, B2, B3 and BR for reverse) - with no one-way clutch and no band brake. Every gear uses exactly three engaged elements, and every shift changes only one of them. That is why the unit shifts quickly and can skip gears under hard acceleration:

The two reverse ratios are not a mistake: in the S programme the transmission engages the shorter ratio and in the C programme the longer one - just as, in the C programme, it pulls away in 2nd when going forward.

The converter lock-up clutch works with controlled slip from 1st gear onwards. On the 7G-TRONIC PLUS the converter has a centrifugal pendulum damper that absorbs engine vibration and allows almost complete lock-up at very low revs - hence the lower fuel consumption, but also the higher load on the clutch itself.

The control (VGS) sits entirely inside the pan: the control unit is mounted on the conductor plate of the electrohydraulic unit and carries the speed sensors for the turbine (n1), an internal shaft (n2) and the output shaft (n3), the selector range sensor (s1) and the temperature sensor. The only link to the car is a single five-pin connector (CAN and power supply). The eight proportional solenoids in the valve body control the working pressure, the elements K1, K2, K3, B1, B2/BR and B3 and the converter lock-up. On a fault the transmission goes into limp mode: with no current to the solenoids the transmission stays in 6th; after the engine has been stopped and restarted, only 2nd and reverse are available, with a noticeable jolt on engagement. A single failed solenoid usually blocks only the gears in which its element is involved.

On the 722.9 the same complaint can have causes that differ tenfold in cost - from an adaptation reset to a new transmission. Diagnosis therefore starts by reading the fault codes, not by draining the fluid.

Typical symptoms:

Step 1 - the fault codes. Read them with XENTRY (Star) or a good multi-brand tool. The speed sensor codes - 0717/0718 (n1), 2767/2768 (n2) and 0722/0723 (n3), on VGS1 units the 2200-2207 series - and code 0705 for the range sensor s1 point to the conductor plate (see the section on it below). The exception is code 0721 (implausible output shaft speed): it can also have a mechanical cause, so on 4MATIC cars check the bearings and the transfer case first. Codes 2783 and 0741, together with more than 10 rpm of slip with the converter locked, point to the lock-up clutch. If there are no sensor codes but the shifts are harsh or delayed, suspect the valve body and the solenoids. Code U1138 on the 7G-TRONIC PLUS refers to the auxiliary electric pump (a rare fault).

Step 2 - the fluid. Check the type (red or blue according to the version), the level at 45 °C and the condition: dark fluid that smells burnt accounts for many harsh shifts, copper shavings in the pan point to wear inside the torque converter (most often the lock-up clutch), and coolant in the fluid (a leaking cooler inside the radiator, most often on the W211 and W212) ruins the transmission and cannot be flushed out.

Step 3 - adaptations and software. For shift-quality complaints without fault codes Mercedes requires a software update, an adaptation reset and a teach-in drive - that cures many of the cold 2-3 jolts. It does not help with a worn converter or a failed conductor plate, and the "pedal and key reset" that circulates on forums does nothing at all.

This is where the most expensive mistakes are made. Units built up to 21 June 2010 run on red MB 236.14 fluid (ATF 134); the 7G-TRONIC PLUS, all AMG versions and the hybrids run on blue MB 236.15 (FE-ATF 134). The two are not mixed and not interchangeable - the blue fluid was developed for the new converter, and Mercedes will reject a warranty claim if the wrong fluid is used. If the wrong fluid has been filled and the car has covered less than 10 km, the unit is drained and refilled. When in doubt about which fluid is correct, the transmission serial number and option code A89 decide. We work with Ardeca MATIC+ Z7 to MB 236.14 and Ardeca MATIC MB15 to MB 236.15.

Service data:

The unit has no dipstick and no filler opening on top (according to workshop reports some Sprinters have a dipstick tube) - it is filled with a pump through the drain plug hole in the pan. Level check: engine idling, selector cycled through P, R, N and D. Fluid temperature is watched on the diagnostic tool (an infrared thermometer on the pan is only a rough guide), and at 45 °C the plug is removed - a thin trickle must run from the overflow tube. For the earliest shallow-pan units older editions of the documentation specify 35 °C - follow the XENTRY instruction for the specific unit. If nothing comes out, the level is most likely low: add 0.5-1 L, let the surplus run out and measure how much has run out. Checking at a higher temperature leaves the unit underfilled, at a lower one overfilled. There is no level sensor, so a slow leak from the front seal can run the unit dry without any warning on the dash.

There are two pans and two filters: up to June 2010 a shallow steel pan with a flat filter, on the 7G-TRONIC PLUS a deeper pan with a triple filter. The deep pan with the triple filter can also be fitted to early units - a worthwhile upgrade at the first fluid change. There is no plastic pan with an integrated filter on the 722.9 (that is the 9G-TRONIC). Order the pan gasket with every change, and a new overflow tube if the old one is damaged. On most models the fluid cooler sits inside the radiator (on the ML, GL and R-Class it is separate); when the radiator is replaced or coolant in the fluid is suspected, check the cooler line seals and the cooler line adapter.

The conductor plate (VGS; Leiterplatte in the Mercedes documentation) is the most frequent cause of limp mode on the 722.9 and has its own Mercedes service bulletin (LI27.50-P-049710). Moulded into it are the Hall-effect speed sensors n1, n2 and n3, the range sensor s1 and the control unit itself (n4). Heat cycling and ageing make the sensors (most often n2 and n3) lose their signal - at first only rarely and when hot, then on every trip, with the limp mode described in the symptom table. The failure appears over a wide mileage range - from 80,000 to 300,000 km - and affects every generation of the plate, most often VGS1 to VGS3 (2003-2013).

The generations VGS1 (2003 to about 2007), VGS2 (about 2006-2009), VGS3 (about 2009-2013, with FBS3) and VGS4 (from about 2013 onwards, with FBS4) are not freely interchangeable (permissible substitutions are determined via EPC and XENTRY); the early 7G-TRONIC PLUS units of 2010-2013 still have VGS3. There are three repair options:

• A new Mercedes plate with SCN coding - the most expensive solution. Before removal the solenoid data and adaptations are transferred from the old plate, and after fitting, the range sensor is taught in; if the car is driven before all steps are complete, the new unit can lock itself permanently.
• Repair of the plate, keeping the original control unit - on VGS2, VGS3 and VGS4 the n1 and n2 sensors are replaced with a speed sensor kit and the range sensor with a new Y3/8s1 range sensor (two variants, 02 and 03, by transmission number); a failed n3 means a plate repair at a specialist. No coding is needed - this is the most common practice.
• A used plate - only with its data erased and with coding.

On VGS1 units and on all AMG versions Mercedes allows only replacement of the complete electrohydraulic unit. Whenever the plate is worked on, the solenoids are tightened to 8 Nm, and the unit is bolted to the housing at 4 Nm + 90°. The white B3 oil feed pipe must be transferred to the new valve body with new seals (without the pipe the unit has no drive), and the valve body screws are replaced if their heads are damaged. After fitting: adaptation reset and teach-in drive.

The torque converter is the second most frequent failure, because its lock-up clutch works almost all the time. The symptoms are those listed under diagnosis: shudder at 1,200-1,600 rpm, a jolt on the 2-3 shift, codes 2783 and 0741. For 7G-TRONIC PLUS units built between April 2011 and August 2015 Mercedes describes a specific cause in service bulletins (LI27.20-P-055758 and LI27.20-P-064558): on the earlier units of that period the converter bush wears because of a rough journal on the input shaft; on the later ones the sealing ring between the shaft and the clutch leaks. The prescribed repair is a new converter, polishing of the input shaft with 15 µm micro-finishing film and a reset of the converter adaptations - a fluid change does not help. On early units the friction lining also wears frequently, and the sign is the same: copper shavings in the pan. If a shallow-pan unit shows a lot of shavings, Mercedes prescribes replacement of the whole transmission, because the debris has already passed through the valve body and the solenoids.

The converter is rebuilt with new friction discs and steel plates for the early type (34 teeth), or with two or three friction discs (196 mm, 40 teeth, depending on the engine) and four steel plates (187.8 mm, 36 teeth) for the 7G-TRONIC PLUS. The sealing rings depend on the type: MB-O-2V and 4V for the early units, 6V, 7V, 10, 11V and 12V for the late ones, while MB-O-5V is common to both. To go with them: a bush, a hub, a snap ring, the MB-FN-2K kit and the Sonnax repair kits; on installation the converter-to-flexplate bolts are renewed. On the AMG SPEEDSHIFT MCT the wet start-up clutch is rebuilt with 12-tooth discs and SRMB17 and SRMB18 sealing rings.

The oil pump is checked whenever there is a leak at the front or a vibration. Later pumps have a bearing instead of a bush, and an old converter hub fitted into such a pump has its surface scored and the pump starts to whine - so the pump and the converter are inspected together. Replace the seal (43 x 58 x 7 mm, shared with the 722.6), the Sonnax bush or - our recommendation for the 722.9 - the more durable bearing, the O-ring and the intermediate plate between the bell housing and the case, which has a latex coating and is renewed every time the unit is opened. On the 7G-TRONIC PLUS removing the auxiliary electric pump also calls for a new oil pipe.

The valve body of the 722.9 is an aluminium block with eight Bosch solenoids that look identical but differ in their characteristics. The blue-cap solenoids (A 220 277 09 98) serve K1, B2/BR, B3 and the converter lock-up, the black-cap solenoids (A 220 277 10 98) serve the working pressure, K2, K3 and B1. Swapping them is a classic assembly mistake. Mercedes allows at most three solenoids to be replaced in one repair, because the control unit stores an individual characteristic for each of them; no coding is needed; after the change the shift adaptation procedure in XENTRY is carried out.

With mileage the bores in which the valves move wear: the working-pressure regulator starts leaking into the pan (pressure drop, poor lubrication and cooling of the converter), and the two supply-pressure regulators feed the solenoids with unstable pressure. The symptoms are harsh shifts or flaring revs on 2-3 (K1) and 4-5 (K3), delayed engagement of D and R and pulling away in the wrong gear - without sensor codes. The answer is a vacuum test of the bores and the Sonnax 88740-01 and 88740-02 repair valves, not a new valve body. On a unit with a worn converter the solenoid screens are checked too - Mercedes names them as a cause of harsh 1-2 and 2-3 shifts on the 7G-TRONIC PLUS.

Every time the unit is stripped, the solenoid O-rings (a cut ring on the tip of a solenoid means a stuck valve) and the valve body O-ring set are renewed. For damaged springs and valves there is a valve body repair kit, and for a leak around the selector shaft its seals are replaced.

The clutch packs of the 722.9 rarely burn out on their own - they are usually ruined by slip from low pressure, a worn converter or fluid diluted with coolant. K1 applies on the 2-3 shift and K2 on 3-4; problems on 4-5 point to K3, and according to rebuild practice the K2 friction discs are the ones replaced most often. A characteristic failure is the K1 bonded piston: the aged rubber leaks and the car drops into neutral when 3rd engages. It is replaced with a new K1 piston (102 x 132 x 18.5 mm) or with a piston kit for K1, B1 and B3; the B1 piston is also available separately. On early units Mercedes updated the bearing between the K1 drum and the pump stator - on such a unit the bearing is checked without fail.

Discs are replaced according to wear - with a friction disc kit and a steel plate kit or individually by pack:

• K1 - single-sided internal-spline discs (189710) and external-spline discs (189711)
• K2 - internal-spline (189706) and external-spline discs (189707)
• K3 - internal-spline (141708) and external-spline discs (141709), shared with the 722.6
• B1 and B3 - shared internal-spline (189700) and external-spline discs (189701)
• B2 and BR - double-sided discs shared with the 722.6: B2 friction disc with 141703 steel plate and BR friction disc with 141705 steel plate

For sealing in an overhaul, use an overhaul kit - with or without pistons and an intermediate plate - or a master kit that includes the discs. Order the sealing ring kit with it - for the stator, the input shaft and the rear planetary shaft - and the stator sealing rings with the K1 O-ring. Bearings to check every time the unit is opened: the front bearing of the rear planetary set, the rear bearing of the K2 shaft, the B1 bearing and the output shaft bearing with its seal and the flanged retaining nut. For corroded bolts we also offer a set of bell-housing-to-case bolts.

4MATIC transfer case. On the C-, E-, S-, CLS-Class and GLK of 2007-2013 the integrated transfer case is the weak point at the rear. The first symptom is a whine that starts quietly and rises with road speed (usually between 60,000 and 150,000 km) - it is often mistaken for a wheel bearing. The second is a leak from the output shaft seal towards the front propshaft. Mercedes sells no internal parts and offers only a complete unit, but the transfer case can be rebuilt: a kit of four bearings, a seal, a housing gasket and a front propshaft cover; and, for a worn centre clutch pack, a complete disc pack or friction discs and steel plates individually. We also stock a used 4x4 output shaft with its gear.

MID Auto keeps more than 140 items for the 722.9 in stock: overhaul kits (Transtec, Precision and master kits), friction disc kits and steel plate kits and individual discs for every pack, bonded pistons, torque converter parts for the early, PLUS and AMG versions, oil pumps and their parts, valve body parts, Bosch solenoids, sensors for the conductor plate, filters, bearings, transfer case bearing kits and Ardeca fluids to MB 236.14 and MB 236.15. Every part is shown in its position on the interactive transmission diagram, and the links in this article lead straight to the relevant product or the corresponding part group.

When ordering, send us the VIN of the car or the full transmission number (722.9xx and serial number) - that is how we determine the version (7G-TRONIC or PLUS, AMG, 4MATIC), the correct fluid, the converter type and the generation of the conductor plate. When repairing the converter, order the pump seal, the bush or bearing, the intermediate plate, the filter and the fluid at the same time, so the car is not left waiting on the lift.

The 722.9 is a transmission with two faces. Its gear train - planetary sets, clutches and brakes - is robust: with regular fluid changes, in our experience, the unit is rarely opened before 250,000-300,000 km. The problems come from the periphery - the electronics in the pan, the torque converter, the transfer case on 4MATIC cars and the fluid - and most of them are repaired at a reasonable cost if caught in time - the expensive exceptions are coolant in the fluid and prolonged driving with metal debris. Most of the gearboxes we have seen written off for replacement turned out to have a failed conductor plate.

Author: Tsanko Doktorov, chief mechanic and technical director of MID Auto. He has more than 30 years of experience and specialises in automatic transmissions, with dozens of certificates from seminars and training courses on the repair and rebuilding of gearboxes, torque converters and valve bodies. The article is based on MID Auto's workshop practice and on Mercedes-Benz technical documentation for the 722.9.