Mercedes-Benz 722.9

Transmission general data

The 7-speed automatic transmission Mercedes 722.9 was produced in 2004 (G-tronic) and considered to be a masterpiece from Mercedes Benz for С-class models. It was used for all RWD Mercedes cars from С180 to С350. This transmission was designed on constructive basis of the 6-th series of automatic transmissions and many spare parts are interchangeable.

• W7X550 - for engines up to 3,5L and 550Nm; ATF capacity - 8,6L;
• W7A700 - for engines up to 5,5L and 700Nm; ATF capacity - 8,9L;
• W7B700 - for engines up to 6,3L and 850Nm; ATF capacity - 9,1L.

Technical issues and repair guidelines

For this transmission, Mercedes engineers used the controlled slipping of the of the torque converter frictions, which starts from the first gear. In many cases, this peculiarity leads to rapid fluid contamination by the torque converter frictions and premature necessity for fluid change and the torque converter rebuilding.

The whole family of 722.9 transmissions is sensitive to issues with fluid shortages and its contamination. The main spare parts in this transmission are wearable teflon rings, which are crucial for accurate gear shifting. There are two types of friction components for this gearbox- one-sided and two-sided.In most cases, frictions of the K2 package get replaced. The K1 frictions are replaced less often as well as K3 frictions, but repair specialists order a full kit of friction discs in case of burnt oil.

The first typical problem of the 9th series is related to the failure of the connector electronic board - the sensor Y3 / 8n1 gets burnt. In most cases, this board is replaced. The resource of solenoids heavily depends on the oil contamination level and leakproofness of packages.The second common problem of this transmission is the damage of the housing bell caused by vibrations from aggressive driving.

The valve body in this transmission operates at temperatures up to 130º and it is very sensitive to overheated and contaminated fluid and shavings. Small springs of the valve body can break down, solenoids may get clogged. Experts assume that abnormal operation of the valve body leads to shortages of oil pressure in the 722.9 unit, frictions get burnt and other problems occur in the chain order. Since Mercedes engineers provided the valve body repair without the transmission removal, thus it is possible to detect the abovementioned problem and solve it by means of reassembly and cleaning.

Problems also occur in the multi-function switch (Servo mechanism module). Although components of this transmission are quite reliable, but problems in the electrical part have a negative impact on the oil pump and consequently result in issues with the rear planetary gear and bushings.The torque converter repair is one more operation which should become a preventive measure to prolong the service life of this transmission.