The original prototype of the Centennial transmission system giant ZF AMT transmission - Soden transmission

The Soden transmission is a four-speed transmission with a constant meshing gear design and a pre-selected gear and synchronizer. The transmission is designed with a pre-selected mechanism that allows the driver to decide in advance which gear to be engaged.

The driver sets the gear that the transmission will shift through a knob on the steering wheel, then presses the clutch and the transmission gear is automatically engaged.

The Soden transmission's effortless shifting had a great technical advantage at the time, but its design was too advanced at the time, the transmission control was too complicated, so it was only produced in small quantities and was not commercialized in the market. application.

Von Soden, inventor of Soden Transmission
Soden transmission
The first car to use the Soden transmission

In the 1980s, ZF developed an automatic pre-selection gear shift system called AVS (Automatic pre-selection gear change system), also known as semi-automatic transmission shifting system. The AVS is a shifting system formed by adding a shifting actuator to a conventional mechanical transmission, called an Add-on system. The following picture shows an automatic preselected shifting transmission system combining AVS and ZF manual transmission 8S-180. As can be seen from the figure, a large number of external components and sensor components and wiring harnesses of the shift actuator are added outside the transmission.

ZF 8S-180 AVS transmission

When the driver is manipulating the AVS system, it operates through an electronic shifter as shown below in the cab. The shifter includes a rotary switch and a control lever. The rotary switch is used to select the driving mode (D: forward, N: neutral, R: reverse), and the lever is used to perform the upshift and downshift operations, correct the starting gear position and shift into neutral.

When the driver performs the shifting operation, first select a gear position. At this time, the gear position of the transmission is not actually engaged, so it is called the gear pre-selection, and the driver pre-selected gear position will be displayed through the display screen. When the driver needs to shift gears, the pre-selected gear will automatically hang when the clutch is depressed.

Such an operation reduces the workload of the driver when shifting gears, and at the same time, the hand does not need to leave the steering wheel when shifting, so that the driver can concentrate on the front road condition, thereby improving the safety of the vehicle.

AVS electronic shifter

Briefly explain why AVS is called a semi-automatic transmission:

When the manual transmission began to automate, the concept of “semi-automatic transmission” was used, which was related to the operation of “engaging the clutch/starting” and “changing the gear”, and one of the two operations was automated. Called a semi-automatic transmission, if both are automated, they can be called a fully automatic transmission.

Since ZF has developed a semi-automatic transmission system, is it possible to develop a fully automatic transmission? The answer is yes, it is ZF's first modern commercial vehicle automatic transmission system: AS Tronic.