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Gearbox noise in the 2016 W212 350d. 96,000 miles. Complete MB SH.

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Greetings, I have previously mentioned an atypical noise emanating from my gearbox when it is in either D1 or R gears.
When choosing any option after P, I experience a creaking sound emanating from the front right corner of the vehicle. However, this occurrence is limited to the first hour of the car's operation. In the event of a roll to a halt at D1, no anomalous noise is observed. The occurrence of this phenomenon is contingent upon transitioning from N to D.
The Mercedes dealership expresses uncertainty on this matter, although having seen the auditory phenomenon.
The retired Range Rover mechanic, who is my neighbour, proposes the presence of an internal valve or pump inside the automotive enclosure.
Has anybody encountered a similar problem? Do the car box have such valves?

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Is the front right of the car located in close proximity to the gearbox or drivetrain, unless it is equipped with a 4matic system?

Are you certain that there is no cracking noise emanating from the brakes while the vehicle is held against the gearbox?

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Certainly. The sound is only perceptible when transitioning from N to D or R. When you apply pressure to the brakes, the action occurs and persists even after you remove them. It seems to cease at velocities beyond 10mph (or maybe other sounds overpower it).
It begins only after the vehicles have been in operation for around one hour, and only after you have interacted with N. If you come to a complete stop, leave it in D (such as a traffic signal) and immediately begin moving forward, it will not occur.
A witness characterises the sound as like the presence of a frog in the engine compartment, emitting croaks at regular intervals. Does not seem to be related to suspension or power steering, since it manifests while the vehicle is stationary.

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Indeed, the gearbox cooler will function as a'saddle' cooler, specifically operating as an integral component of the primary engine cooling radiator. The presence or absence of a thermostat in the system is uncertain, since my knowledge of your car/model is insufficient to determine.
I am inquiring if there is an issue or whether your oil level is little depleted. In a general sense, the air-to-fuel (ATF) transfer occurs from the torque converter, which serves as its primary heat input, to the cooler. When a directive is sent for the gearbox to perform a certain action, such as transitioning from N to D, oil is extracted from the pressure circuit (which supplies power to the torque converter) in order to facilitate the selection of gears. If the flow to the cooler is hindered, it might result in a decrease in pressure (or total deprivation), leading to the occurrence of noise in the exterior piping to and from, or inside, the cooler.
It should be noted that the aforementioned statement is a generalisation and the configuration of your gearbox may vary. However, I would first assess the fluid level. Perhaps focusing on the cooler and listening to its sound might provide further information. When assessing the fluid level, it is important to observe for any signs of excessive foaming in the oil. Noise may arise due to air entrainment, which occurs when air enters the suction line between the oil pan and the pump. It is unlikely that it would hinder the working of the torque converter, but it is not impossible. However, if this occurs, it may be unnoticed as most torque converters are operated with the clutch locked. If it does occur, it should be addressed promptly, which is a task that any skilled garage could do.

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Thank you, norbury.brook, for providing this comprehensive summary. Many of the suggestions you are making are above my technical expertise, but they do provide me with some guidance to share with my garage as a potential problem.
I may propose something for them to examine, therefore creating a sense of obligation for them to do so. I have a high level of satisfaction with my 350d 212 and am willing to invest in maintaining it in excellent shape. However, I am concerned about the gearbox difficulties, since many garages are hesitant to address this issue.
Thank you for dedicating your time to share.

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