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Greetings, everyone.
The subject of discussion pertains to a 2006 CLK 350 vehicle.

When decelerating while descending a slope at around 30 miles per hour, a significant jolt is experienced during the transition to third gear, like a minor rear-end collision.

Has this phenomenon been seen by others?

The lubricant has been recently replaced, and all other gears are operating well and without issue. There is a lack of visible codes.

Do all hills or just certain hills fall under consideration? Occasionally, my W209 vehicle exhibits this behaviour, particularly while traversing certain inclines. However, my 9-3 also exhibits this characteristic. In addition, there were one or two Lexus vehicles in the past. The observed phenomenon may be attributed to a confluence of factors, namely reduced velocity, deceleration, and an upward slope.

What is the current mileage of your vehicle?
Was the automobile exhibiting this behaviour prior to the fluid change?
Did the issue arise immediately upon the alteration of the fluid?
By whom was the service performed?
Was the appropriate fluid and filter utilised?
Is the gearbox oil level at the appropriate level?
Could you please confirm if this gearbox is the 5th generation (5G) or 7th generation (7G) model?

Thank you for your prompt response.

The topic under discussion pertains to the concept of seven-speed.

The vehicle has reached a mileage of 101,000 miles.

A gear box service was performed on the vehicle around 15,000 miles ago, coinciding with its purchase. It is my understanding that the prior owner had experienced similar issues with the gear system.

Based on my understanding, appropriate fluids were used and the fluid level is satisfactory. The Indianapolis (Indy) products employed have consistently shown high quality, since they have been a preferred choice for an extended period of time.

The temperature of the gearbox fluid remains within an appropriate range, typically about 75 degrees Celsius, while operating under high temperature conditions.

The aforementioned alterations are satisfactory, with the exception of transitioning to the third gear when decelerating on a downward slope at around 26 miles per hour.

It is peculiar.

It seems that there is no other method for inspecting the gearbox fluid except than doing a complete drainage.

Prior to beginning the descent down the hill, it is advisable to transition to a lower gear denoted as "S." The purpose of engaging the "S" gear is to provide a smoother and more controlled descent. The acronym PRNDSL stands for Park, Reverse, Neutral, Drive, Slope, and Low. Furthermore, using a gentle acceleration and braking technique allows for a seamless half throttle downshift, devoid of any abrupt movements. Additionally, it is advisable to maintain the vehicle's position on an incline until the descent of the hill has been completed.

The cessation of gasoline consumption occurs when the accelerator pedal is fully released, since no fuel is introduced into the engine under such circumstances.

At some point, all automated vehicles will exhibit similar behaviour if allowed to operate autonomously. similar is precisely why the gear selector is included, since it is crucial to familiarise oneself with the vehicle's attributes and techniques to prevent such occurrences.

Thank you, sir.

Unfortunately, the slope feature is not available on my device. Typically, I like to keep it on regular mode rather than comfort mode.

My present practise involves manually maintaining the gearbox in the third position when I anticipate the occurrence of the aforementioned situation.

It is noteworthy to acknowledge that this occurrence is rather common.

It may be inferred that if an independent mechanic performed the task, we can exclude the possibility of the gearbox servicing or fluid being a contributing factor.
Indeed, it is possible to do a level check on the 7g, but it is essential to possess the requisite knowledge and expertise when undertaking the task of opening the sump plug. However, it is worth noting that such a procedure should ideally be avoided in most cases.
Regarding the act of shifting gears abruptly when descending a slope, it is noteworthy that neither my 130,000-mile 7th generation gearbox nor my 100,000-mile 5th generation gearbox exhibit this behaviour.
I am curious about the potential consequences of manually downshifting gears when descending a challenging incline.

The act of manually decreasing is acceptable.

The matter at hand is peculiar.

Upon more experimentation, it seems that the phenomenon in question may really be a consistent occurrence.

It is acceptable to engage in manual insertion. Upon observing the revolutions per minute (RPM) prior to the gear change, it is hypothesised that the transition may include a straight drop from fifth gear to third gear. Regarding the topic of hens, it is worth noting that hens are a common domesticated bird species that are often raised for One has difficulty in maintaining equilibrium between the act of braking and the amplified forward movement when descending a slope.

It is observed that there is a little roughness in the vehicle's performance while engaging in mild acceleration and manually shifting to the third gear without raising the throttle.

Engaging in coasting and thereafter transitioning to third gear manually or executing a forceful downshift is deemed acceptable.

It is peculiar.

As inferred, the automatic gearbox has the capability to downshift by two ratios while it is essentially not under stress.