The 722.6 gearbox has abrupt movements in 3rd gear when it is cold.

[CyberNinja]

Hello. My W211 vehicle, equipped with the 722.6 gearbox, began experiencing abrupt movements when in 3rd gear as the temperature dropped. This behaviour occurs only at low temperatures and specifically while the vehicle is in the third gear. The transition between ratios is satisfactory, but, there is a noticeable jerking sensation while the vehicle is in 3rd gear, similar to the feeling of insufficient throttle input when releasing the clutch in a manual gearbox automobile. If the issue is caused by either the torque converter or the lock up solenoid, it should occur in any gear, correct? Any recommendations on the potential cause of this issue, and if it can be detected with the appropriate MB diagnostic tools, would be appreciated.

[Geek2232]

Have you verified the amount of Automatic Transmission Fluid (ATF) and determined the date of its most recent change?

[CyberNinja]

The fluid was replaced one year ago and it remains the correct colour and at the appropriate level.

[bvlenci]

Have you verified the ATF level when the vehicle was at operating temperature (after a 20-minute drive), with the engine running, and on a flat surface?

[CyberNinja]

Examined on a flat surface at both high and low temperatures.
If the issue is caused by gearbox fluid, it would manifest in every gear and result in a delay in acceleration, rather than a sudden jerking in a specific gear.

[PixelMaster]

Will the issue resolve itself if you apply much more pressure? It is possible that the issue lies with either the conductor plate or the oil seal on the multi plug.

[CyberNinja]

Affirmative, it does. It is the same when the oil becomes heated. The issue is resolving itself at a rate of 95%.

 

[PixelMaster]

The symptoms described suggest that the issue may be related to the conductor plate. Initially, the problem may manifest in one gear, but with time it tends to deteriorate. My launch diagnostic did not provide any results, however maybe other kinds of diagnostics can provide more information. I had the issue diagnosed at my nearby Mercedes shop, but the diagnostic test did not reveal any problems. However, to be honest, they cannot be relied upon to adequately secure the wheels in that place.

[PixelMaster]

Consider the possibility of another identified defect in which the oil cooler may allow coolant to seep into the gearbox. It would be advisable to have this matter inspected, if possible.

[CyberNinja]

ok,thanks all😇