Is it the user's or the manufacturer's responsibility? Explanation of the Land Rover 9AT gearbox "failure"

In fact, the exposure of the 315 Gala did not cause much damage to the Land Rover Aurora. On the contrary, taking this opportunity, the domestic Land Rover Aurora successfully lowered its price. As the number of vehicles in the market increased, this car also began to establish a good reputation and gradually became a so-called "street car".

Of course, for all the consumers who are waiting and watching, the 9AT gearbox equipped in Land Rover Aurora and Discovery Sport is still the most important issue for them, even more than the four words "Chery Land Rover". As an aside, I am not advertising for Land Rover, but the domestic versions of Aurora and Discovery Sport are more cost-effective than imported cars, and even better in quality.

After its launch, ZF's transverse 9AT gearbox was installed on the Land Rover Aurora and Jeep Cherokee. However, both vehicles had transmission problems caused by the gearbox. As the world's most advanced transverse gearbox, does it really have design flaws? The answer is no.

Let's talk about the Jeep Cherokee first. The transmission complaints of this car are mainly concentrated in North America, and the feedback is that there are serious setbacks and delays when shifting gears. This problem has actually been solved. The cause is a programming problem of Chrysler, not a design defect of the transmission.

As for Land Rover, the problem is completely different. According to the feedback from domestic Aurora and Discovery Sport owners, the problems with Land Rover's 9AT gearbox are mainly power interruption and instrument panel fault codes. The specific manifestations are:

When the car stops at a red light, the engine automatically shuts down in the automatic start-stop mode. Car owners who encounter this problem will habitually switch the gear from D gear to N gear. Wait for the red light, and after a few dozen seconds, the green light will turn on, and the gear will be switched back to D gear. Release the brake, and the engine will automatically ignite, but the car will not move when the accelerator is pressed, and the engine will rotate. At this time, the dashboard shows a gearbox failure.

Is there really a malfunction? Such a common automatic driving habit can cause trouble for one of the most advanced transmissions in the world? The answer is of course no.

Before answering this question, let's first look at why many car owners like to switch to N gear when parking. For traditional automatic transmission models, if there is no automatic start function or the function is turned off, switching to N gear when waiting at a red light can disconnect the engine and the gearbox. The advantage of this is that you don't have to step on the brakes for a long time and protect the gearbox.

So why doesn't Land Rover's 9AT work? And why doesn't the same happen to the Jeep Cherokee, which is also equipped with this gearbox? The reason is actually very simple.

When you stop at a red light, the engine automatically shuts down. At this time, the connection between the engine and the gearbox has actually been automatically disconnected, but the gear position display is still in D gear. The correct operation method is to either keep your foot on the brake (short red light) or press the automatic parking button. It should be noted that the automatic parking and electronic parking brake of Land Rover Aurora and Discovery Sport are integrated.

At this time, the owner switched the gear to N gear again. Then, when the green light came on and the gear was switched back, the gearbox that was originally disconnected when the engine was turned off was actually connected, and the gear shift could not be completed because there was no oil pressure when the engine was turned off. That is, even if you switched the gear to D gear, the gearbox did not actually complete this physical operation.

It's very simple, because the engine is turned off, and the gearbox needs oil pressure to shift gears, and the oil pressure comes from the oil pump driven by the engine. At this time, the engine is turned off, and no matter what gear you switch to, you can't really shift gears. Therefore, after releasing the brake, the engine ignites, but there is no transmission power connection at this time. This is why the car doesn't move when you step on the accelerator.

But you may ask, other models also have automatic start-stop function, and when it is turned on, the engine is turned off, and the gear shifting does not affect the start. This is because the Land Rover Aurora and Discovery Sport use knob-type electronic shifting. Jeep Cherokee uses mechanical shifting. Even if there is no engine to provide energy, manual shifting can create oil pressure to achieve gear switching by directly shifting with the help of power.

Therefore, the real problem of Land Rover's gearbox is the conflict between the electronic knob shifting method and traditional driving habits. In addition to the mechanical power shift lever, there are currently four main types of mainstream electronic shift levers:

One is represented by BMW. The electronic shift lever matched with BMW's ZF 8AT gearbox is a representative work of this type of shift lever. When waiting at a red light, BMW cars can automatically park through the Autohold function. Even if low-end models do not have an Autohold button, the gear design of its shift lever generally means that car owners will not switch to N gear.

The second is represented by Mercedes-Benz. The hand-shift gearbox matched with the Mercedes-Benz 7G-Tronic is the most advanced one among the hand-shift gearbox models. Generally, Mercedes-Benz cars have the function of automatic parking by stepping on the brake deeply, so they will not shift to the N gear. Even if there is no automatic parking, the same as BMW, this kind of automatic return electronic gear lever is not suitable for shifting to the N gear when parking. Engineers have taken this situation into consideration when designing.

The third is represented by Aston Martin. Some models of Aston Martin use push-button shifting. If you haven't known about it, then the push-button shifting used on Lincoln MKZ and MKC should be more familiar. This shifting method is the simplest and most direct. Then you may ask, if the Lincoln car is switched to N gear with the engine off, when ignition is turned on, won't the situation of Land Rover also occur? No. Because Lincoln's EcoBoost engine and SelectShift transmission will not automatically disconnect after the engine is turned off.

The fourth is represented by Jaguar Land Rover. Currently, Jaguar XE, XF, F-Pace, Land Rover Aurora, and Discovery Sport are all equipped with the knob-type shift device developed by Jaguar Land Rover. Why doesn't Jaguar have this situation? Because it matches the software setting of ZF's 8AT longitudinal gearbox, which is different from the 9AT.

ZF's 9AT programming is divided into two parts: one is the underlying logic of the gearbox, such as determining whether to enter the protection mode, etc.; the other is the program set by the vehicle manufacturer to adapt to its engine, which is used to determine the throttle depth, engine speed, etc., to determine the upshift and downshift. The problem encountered by the Land Rover owner is caused by the first part of the underlying programming: when the engine is ignited, the knob is in D gear but the gearbox is not connected, the program determines that the gearbox is faulty.

Therefore, the failure of Land Rover's 9AT gearbox is ultimately caused by the conflict between its program settings and driving habits. This "squeamish" software setting is related to the mechanical structure of this 9AT gearbox. Tencent Digital's previous gearbox series articles have introduced that ZF's 9AT uses 2 sets of claw clutches and 4 brakes to achieve gear shifting.

The engagement speed of the dog clutch is faster than that of the multi-plate clutch, but it is also due to this design that after the vehicle is completely stopped, in order to protect the gearbox, the dog clutch in 1st gear will be disconnected, and the connection between the engine and the gearbox will also be disconnected. However, at this time, the shift knob still shows that it is in D gear.

The correct way to operate at this time is to pull the electronic handbrake (integrated with the automatic parking brake) and then release the brake. When the green light comes on, just step on the accelerator to start the engine. Therefore, it is completely unnecessary for car owners who encounter problems to manually turn the gear to N gear at this time.

Whether this is a design problem or a result of driving habits, each has its own reasons. In short, for any automatic transmission model, it is necessary to develop good operating habits. For the mechanical power-assisted shift lever, although it is more durable and will not give out fault warnings at every turn, in fact, its mechanical structure is suffering from serious wear and tear under your destruction, but you just can't see it.

As a winner of Toutiao's Qingyun Plan and Baijiahao's Bai+ Plan, the 2019 Baidu Digital Author of the Year, the Baijiahao's Most Popular Author in the Technology Field, the 2019 Sogou Technology and Culture Author, and the 2021 Baijiahao Quarterly Influential Creator, he has won many awards, including the 2013 Sohu Best Industry Media Person, the 2015 China New Media Entrepreneurship Competition Beijing Third Place, the 2015 Guangmang Experience Award, the 2015 China New Media Entrepreneurship Competition Finals Third Place, and the 2018 Baidu Dynamic Annual Powerful Celebrity.