DIWA Transmissions for buses | 70 years of efficient standard

In response to the growing need for effective and ecologically friendly driving solutions, Voith developed the mild hybrid system. It bridges the gap between alternative solutions and diesel engines.

Heidenheim, Germany- Nearly 400,000 city and intercity buses have DIWA automatic transmissions installed as of this writing. The smooth and quiet ride, made possible by the stepless starting and braking mechanisms, is appreciated by the passengers. Operators have used DIWA technology for many years because it has lower fuel consumption, which results in lower emissions, as well as low maintenance costs.

These properties also largely correspond to the arguments Voith used to promote and launch of the first DIWA model at the IAA in Frankfurt in 1953. While the emission of pollutants did not play a key role 70 years ago, the benefits of fuel savings, efficiency and low servicing requirements were already attracting the interest of OEMs and bus operators in that era. In the same year, a DIWA production facility was opened at Voith headquarters in Heidenheim. This was followed in 1963 by a transmission plant in Garching near Munich.

The transmission system's great efficiency and related cost effectiveness were based on the gearbox's working theory. The differential torque converter, which gives the DIWA gearbox its name in German (Differenzialwandler), divides the engine power into hydraulic and mechanical power branches. The engine constantly runs in a favorable fuel consumption range because the gearbox automatically offers the best transmission ratio for each driving circumstance.

With its DIWA transmission, Voith revolutionized the bus industry. Demand was therefore great. The Berliner Verkehrsbetriebe (BVG), a public transportation provider in Berlin, was one of the company's first significant clients. This was the beginning of a close alliance between the two businesses that has lasted up to the present. The technological company with its headquarters in Heidenheim not only installs DIWA transmission systems on the city's buses, but it also serves as the DIWA transmissions' service center.

Over time, an increasing number of bus operators and OEMs have turned to Voith's transmission technology. Outside of Germany's boundaries, the advantages of the DIWA automatic transmission are well known. Italy and the UK were Voith's two most significant export markets in the early 1980s.

Over time, Voith has continued to hone the DIWA concept, adapt it to changing market demands, and include cutting-edge technologies. A new version of the system, the DIWA 851 was shown at the IAA in 1973, and its hydrodynamic counter-rotating torque converter operating mechanism is still in use today. This was the first time an electronic control system has been applied to a transmission in a commercial vehicle. In 1976, a fourth gear called overdrive was developed. It lowers the engine rpms from a certain speed to allow for more frugal running at a high ultimate speed. The most recent DIWA model has seven gears, a second overdrive, and a distinct secondary retarder.

Fuel consumption was decreased with each subsequent generation, and modifications were made to handle ever-higher engine power. As one of the top transmission manufacturers for the bus market, Voith invented start-up management and start-stop technology, which are now just as much a part of the scope of supply as clever gear-shifting programs. Stop-start technology enables a significant reduction in fuel consumption, with fewer noise and exhaust pollutants as a result, especially in city traffic where buses spend up to 40% of their working time in idle mode.

Since 2022, Voith has been utilizing DIWA NXT, the most recent version of automatic transmission system, to outfit city and intercity buses and coaches globally. In response to the growing need for effective and ecologically friendly driving solutions, Voith developed the mild hybrid system. It bridges the gap between alternative solutions and diesel engines.

Both drivers and passengers praise the DIWA NXT's ability to provide a comfortable ride and its continuation of earlier transmission systems' traditions. While this is going on, fleet operators profit from up to a 16 percent reduction in fuel use. The DIWA NXT provides affordable maintenance and service charges, much as all generations before it. As well as providing digital upgrades, monitoring, and service tools like OnEfficiency, Voith also does.SmartAccelerate. By using these instruments, the individual operators may streamline maintenance and increase the operational efficiency of their vehicles.

The DIWA NXT automatic transmission will be highlighted by Voith at Booth 520 in Hall 5 at Busworld Europe 2023 under the theme "Tradition meets Innovation" when the event is scheduled to take place in Brussels from October 7–12, 2023. On October 10 at 16:00, you are cordially invited to join Voith in commemorating the 70th anniversary of DIWA transmission technology. Additionally, Voith will be displaying the most recent iterations of their ground-breaking electrical drive concept, VEDS, which is now well-established in the bus market.