The gearbox lowers to third gear while braking downhill, causing a horrible jerk.

[BenTrevor]

Greetings, everyone.
The subject of discussion is to a 2006 CLK 350 model.

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

Has this phenomenon been reported by other individuals?

The fluid has been recently replaced, and the remaining gears are operating well and without issue. There is no display of any codes.

[Chrishazle]

Do all hills or just certain hills fall under consideration? Occasionally, my W209 vehicle exhibits this behavior, although it is limited to certain inclines. However, my 9-3 also exhibits this characteristic. Additionally, there were one or two Lexus vehicles in the past. The observed phenomenon may be attributed to a confluence of factors, namely reduced velocity, the use of brakes, and the presence of an incline.

[Darrellll]

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

[BenTrevor]

Thank you for your prompt response.

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

The vehicle has accumulated a mileage of 101,000 kilometers.

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 also had this issue.

Based on my understanding, appropriate fluids were used and the fluid level is satisfactory. The Indianapolis (Indy) products that I employed have consistently shown high quality, since I have relied on them for an extended period of time.

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

The aforementioned alterations are acceptable; however, transitioning to the third gear when decelerating on a downward slope at around 26 miles per hour.

It is peculiar.

It seems that there are no other methods available for inspecting the transmission fluid, except from the process of emptying it.

[Allan8932]

Prior to starting the descent down the hill, it is advisable to transition to a lower gear denoted by the letter "S". The purpose of engaging this gear is as follows: 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 systems will exhibit similar behavior if they are solely reliant on their own operations. similar is precisely why the presence of a gear selector is necessary, as it entails understanding the vehicle's attributes and acquiring the knowledge to prevent such occurrences.

[BenTrevor]

Thank you, sir.

Unfortunately, my box does not include the feature of slope adjustment. As a preference, I often choose to maintain it in regular mode rather than comfort mode.

My present practice involves manually maintaining the transmission in third gear when I anticipate the occurrence of the above situation.

It is reassuring to learn that this is an often seen phenomenon.

[Darrellll]

It may be inferred that if an independent mechanic performed the task, we can exclude the possibility of the gearbox servicing or fluid being the cause of the problem.
Indeed, it is possible to do a level check on the 7g, although with the prerequisite knowledge and expertise to properly handle the sump plug during the process. However, it is worth noting that, as previously said, such a procedure should ideally not be required.
Regarding the act of shifting gears abruptly when descending a slope, it is worth noting that neither my 130,000-mile 7th generation transmission nor my 100,000-mile 5th generation transmission exhibit this behavior.
I am curious about the potential consequences of manually downshifting gears when descending a challenging incline.

[BenTrevor]

The act of manually decreasing is acceptable.

The matter at hand is peculiar.

[BenTrevor]

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

It is OK to manually insert the item. Upon observing the revolutions per minute (RPM) prior to the gear change, it is hypothesized that the transition may include a straight drop from the fifth gear to the third gear. In the context of poultry farming, the term "hen" refers to a female chicken that is typically raised for egg production. One has difficulty in maintaining equilibrium between the act of braking and the amplified forward movement when descending a slope.

It has been observed that there is a noticeable roughness in the vehicle's performance while engaging in a little acceleration and thereafter manually shifting to the third gear without disengaging the accelerator.

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

It is peculiar.

[MrGreedy]

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