Spares for Classic Cars:
The S 5-20 Project

Back to the Future

• ZF Friedrichshafen AG, the automotive supplier, reproduces the S 5-20 transmission in a one-time edition
• Long-term reproduction of repair kits for wear parts of this transmission

The 'reproduction' S 5-20 project was concluded successfully: On the basis of original spare part kits, ZF is now also offering the option to changeover the 4-speed to a 5-speed transmission. And many customers, who were looking for more riding/driving comfort and fun with lower speeds and economic fuel consumption, have already filed their orders. Moreover, the respective repair kits are provided including the corresponding synchronizer, bearing, and seal/gasket sets. These components have also been installed i.a. in various Maserati vehicles such as the Mistral (6-cylinder version) and also in the 4.2 liter version of the Quattroporte GT.

Every single transmission is professionally, manually assembled and tested on a test bench for a functional test run. For production, latest machines and manufacturing technologies like heat and surface treatment processes are used. The quality tests are also conducted with the latest measuring and test processes. Deliveries are scheduled for January 2012.

In order to secure spare parts supply for the transmission in the future, ZF will keep the most important wear and spare parts available for this unique reproduction.

Back then, the S 5-20 was designed with two shafts (main and countershaft), the classic approach. Both, the main and the countershaft were designed with a large cross-section, as a massive solid construction. All in all, the S 5-20 was considerably smaller than comparable transmissions of that age and thus, represents a compact and solid design requiring a rather small installation space.

At those days, such a short installation length caused a sensation: in comparison to the drives back then, a lot of power was transmit via the output flange and the propshaft to the wheels. For the S 5-20, output train length adjustment was achieved through the propshaft and not the transmission components.

Moreover, the transmission excels via its stable gray cast housing. The gears have a solid, basic cross-section and the needle bearings feature a large diameter. Consequently, people termed the S 5-20 revolutionary - in hindsight, it was definitely 10 years ahead of the transmission developments of its time, in terms of its dimensions. At that time, Karl-Heinz Bordowsky, the transmission design engineer, came from Porsche to ZF and focused very strongly on standardization when designing the components. In those times, standardized bearings for the input and output end were not very common. In the case of the S 5-20 it was also the use of identical synchronizer rings that significantly reduced parts variety.

All in all, the S 5-20 was produced between 1964 and 1976. It was offered as an option for the models 230 SL, 250 SL, 280 SL, as well as the 300 SE, SEb, and SEL for a price of DM 1200. In total, quantities amounted to 3664 units. The transmission was supplied to Maserati with an aluminum housing; the basic concept of the design however was identical for the two transmision variants.