The Most Unusual Car Transmissions

Progress of the automotive industry brings changes not only to the design of modern vehicles, but also affects the structure of car components, and gearboxes in particular. Today it’s hard to surprise auto enthusiasts with unusual transmission solutions, because modern transmissions have similar design and mainly differ in performance charactersitics. And only few people know about transmission concepts which were popular 70-90 years ago. For men of today, these gearboxes may seem very unusual and weird, but even now some gearboxes that date back to those years are quite competitive in comparison with modern transmissions. But it doesn’t mean all modern transmission solutions lack remarkable design and performance features. Therefore, in this article we will review the most peculiar retro and modern transmission solutions and their main features.

DAF Variomatic

Variomatic is considered to be the first economically viable CVT designed by the Dutch car producer DAF. This transmission was released in 1958 and was firstly installed in DAF 600. Variomatic was based on the double rubber V-belt mechanism. Initially this CVT could be mounted on light-duty vehicles, but further improvements of rubber V-belts made them suitable for engines with the capacity up to 1.4 liters. This transmission was adjusted for optimal engine performance thanks to flawless synchronization. Despite the fact that Variomatic was developed long time ago, this CVT operated much better and more efficiently than many modern CVTs. VARIOMATIC transmission is a bright example for any car manufacturer, because this CVT shows how all modern continuously variable transmissions should operate.

Saxomat

Saxomat is a tradename of the automatic clutch drive system manufactured by Fichtel & Sachs AG, which was available as an option for a number of European cars during 1950-60s, including Fiat 1800, Saab, Volkswagen Beetle, Borgward, Goliath, DKW, BMW, NSU, Glas. The Saxomat system had two clutches: 1-st – a standard clutch with pneumatic driving actuator, 2-nd - centrifugal clutch, which automatically switches off when the engine drops to the minimum. Driving a car with a semi-automatic transmission Saxomat felt like something between driving a car with manual and automatic transmissions.

Vehicles equipped with Saxomat transmission didn’t have a clutch pedal. There were only 2 pedals in Saxomat transmission – a brake pedal and an acceleration pedal, as on cars with an automatic transmission, however, the driver still had to shift gears manually. The clutch operation was controlled by a complex electro-pneumatic unit represented as a system of electrically-controlled valves. This unit was controlled by a position sensor (microswitch) of the gear lever and carburettor throttle.

To move the car with Saxomat transmission from a standstill, it was required to shift the transmission lever to the first gear (the clutch was turned off automatically when the gear stick was engaged) and press the acceleration pedal (to release the clutch), after that the calibrated valve in the control unit was activated, gradually filling the diaphragm mechanism chamber with air, so the clutch was smoothly released and the car started off without jerks. While driving, a driver shifted gears in a common fashion, but without pressing the clutch pedal. It was required to turn off the clutch by engaging the lever and then turning it on by pressing the accelerator; gear shifting was performed smoothly without jerks. The system allowed the use of the engine braking. The car with Saxomat could be completely stopped, as in auto transmissions, without switching off gears. It was enough to press the accelerator again to get started. This operation mode was especially convenient for movement in traffic jams.

The Saxomat car transmission was very similar to the Autostick (which we will review later) transmission. The main difference between these gearboxes is that Saxomat used a centrifugal clutch. Saxomat was designed after the Second World War so that disabled war veterans could drive cars without a clutch pedal.

The following video demostrates Saxomat transmission in action

Volkswagen Autostick

The tradename Autostick has been given to a VW semi-auto gearbox and a system developed by Chrysler, which ensured manual gear shifting in the automatic gearbox. Another similar system designed by Porsche is called Tiptronic. VW offered its solution on the market of transmissions in 1968 and was also known as “Volkswagen Automatic Stickshift”. This peculiar semi-automatic gearbox was equipped with a vacuum-operated automatic clutch, which automatically became disconnected when the driver started using the gear stick. This gearbox had four gears (3+1). In other words, the car didn’t have the clutch pedal. This gearbox also had a torque converter which operated with the help of ATF and helped the car to stop or start in any gear. Firstly, Autostick transmissions were installed in VW Beetle and Karmann Ghia.

Preselector gearboxes

The 1-st preselector gearbox was manufactured in the 1930 and quickly acquired popularity among auto enthusiasts. Therefore, this type of transmission was installed in many cars to attract potential customers. An interesting feature of preselector gearboxes of that time lied in the fact that in order to change gears, the driver had to preselect required gear, then he put the clutch in and the gear would get changed. But gradually, due to low reliability and expensive car transmission repair, preselective gearboxes were outcompeted by more efficient transmissions and were forgotten for some time.

Check out the car of the 30-s with a preselector gearbox

Since the mid 90’s, VW revived a long-forgotten technology and began developing its own version of the multi-disk automatic transmission named as DSG (Direct Speed Gearbox) introducing some modifications in the basic concept. And as a result, VW has started installing new commercial-type transmission on Golf Mk4 R32 since 2003. The experiment turned out to be so successful that other automakers also showed much interest in the DSG technology. VW still uses DSG transmission for many VW cars and constantly updates it with new features.

In DSG the transmission control module (TCM) is responsible for the clutch control and gear shifting. This unit consists of electronic and hydraulic control modules and sensors. This unit is named as Mechatronics and is located directly in the transmission housing. Built-in sensors monitor the gearbox condition and keep track of performance of main transmission components. The list of tracked parameters includes input and output RPM (revolutions per minute), the level of oil pressure and temperature, position of selector forks. Mechatronics implements the transmission control algorithm on the basis of signals from sensors.

Currently, there are 6-speed and 7-speed modifications of DSG transmissions. The 6-speed modification is a dual clutch “wet” transmission, where the clutch is constantly placed in oil, which provides lubrication of transmission parts and cooling of discs. This technical concept increases the service life of transmission. The 7-speed DSG transmission, named as “dry”, requires three times less oil than “wet” transmission. In the 7-speed DSG transmission the oil pump with hydraulic drive is replaced with the electric one, which allows reduction of power consumption and fuel economy enhancement of the engine, but the clutch resource will be lower.

In the following video you can learn some useful information about DSG transmissions

Chain transmission from Frazer Nash

The British automobile company Frazer Nash managed to achieve some significant results for its relatively short history from 1924 to 1960. During this time the company released several sport cars and even participated in the well-known race 24 Hours of Le Mans (the best result was 3-rd place in 1949). But the main masterpiece of Frazer Nash was the sports car Serbing released in 1954 (the max. speed exceeded 225 km/h).

A distinctive feature of Frazer Nash cars was an original transmission. In fact, it operated like a chain mechanism on a bicycle. For example, Frazer Nash TT Replica had a simple frame with straight side-members, hard cantiliver leaf springs and a simple steering mechanism. The cardan shaft connected the engine to the rear axle, the drive gear of which consisted of a set of chains with gear clutches of different sizes. This mechanism was so simple that critics of Frazer Nash often did not believe in its high efficiency. In addition, all parts of this car transmission were not protected by any cover and often required cleaning and lubrication. The occurrence of frequent breakdowns was compensated by simplicity of their repair. Excellent traction performance was guaranteed by the design solutions.

Thanks to this chain transmission and its light weight Frazer Nash car could easily accelerate and were very competitive in racing. Another advantage of this car transmission was its high adjustability to operating conditions. Literally, it required several minutes to adjust the transmission for racing or make it comfortable for driving in city traffic.

eCVT in Toyota Prius

Immediately after its release Toyota Prius was harshly criticized in all parameters from design to performance characteristics. Special attention was given to the transmission, which was considered to be a travesty of CVT and a major source of car transmission problems. But with time, Toyota Prius turned out to be one of the most popular hybrid vehicles. As far as Prius transmission is concerned, eCVT proved to be more reliable than most of current transmissions, including common CVT transmissions.

People should not confuse eCVT and CVT, because these are completely different types of transmissions. A standard CVT consists of a belt that combines two conical pulleys to change gear ratios. The eCVT, in turn, has one planetary differential, so it would be correct to call it the planetary gearbox. The most important advantage of the transmission with a planetary gearset is its reliability, because there is practically nothing to break. The transmission itself consists of no more than 20 parts, while a standard transmission includes more than 100 parts. The resource of this transmission may reach up to 1 000 000 kilometers. The list of eCVT advantages includes the following: noiseless operation, fuel economy, high efficiency, and easy servicing.

Brinn two speed transmission

The 2-speed Brinn transmission is considered to be the most popular sports transmission in the world. The first gear is needed to move the car from a standstill. The second gear almost directly transmits the torque to the wheels via the straight shaft. Such transmission design allowed engineers to significantly reduce not only the overall weight of the transmission (22 kilograms), but also the weight of rotating transmission parts that made sports cars much faster. The gear clutch and special design of this gearbox offers reliability and smooth shifting without any special shifters.

Brinn transmissions are usually made of magnesium or aluminum. This transmission is not complicated and requires minimal maintenance. This gearbox can be repaired with the help of standard tools. There are no welded components in Brinn transmissions. All transmission components are cast or made from billet. The process of gear shifting is quick and easy-to-implement thanks to the fact that a driver only needs to move a dog ring to activate direct or low gears. There are no gear teeth on the dog ring to come into contact with other gears.

Informative video about Brinn transmissions

Lenco

In 1970, Leonard Abbott founded his company LENCO Racing Transmissions and after some time the company released 2-speed gearbox. This transmission was gradually upgraded and became the basis for subsequent 3,4,5, and 6-speed gearboxes. LENCO transmissions have found a wide application in the world of motorsport, namely drag racing, as well as in the boat racing . In addition to transmissions, the company produced reduction units and clutch couplings. The main peculiarity of these racing automatic transmissions is that each lever of this gearbox controls a separate gear.

LENCO transmissions consist of several series-connected planetary reduction gears (from 1 to 5) and a clutch unit with forward and reverse gears. Each “module” (gear) has its own lever and two ratios (higher and lower). The clutch in this car transmission is used to move the car from a standstill when it is required. Lenco produces not only manual transmission, but also automatic transmission solutions. In automatic transmissions engineers installed the torque converter instead of the clutch, and the gear shifting system consisting of servo actuators.

The range of LENCO transmissions includes 3 classes:

• CS1 – 5-speed transmissions with standard design which were developed for very powerful cars and boats with highly turbocharged engines running on nitromethane; transmissions of this class can operate with engines, which have the power up to 3000 hp.
• CS2 – 5-speed transmissions which have more compact size and capacity to work with engines, which have the power up to 2500 hp. Users of this class of transmissions may choose from 12 different first gear ratios.
• CS3 – light weight transmissions intended for cars weighing up to 1224 kilograms. These transmissions can operate with engines, which have the power up to 1800 hp.

That’s how LENCO transmission operates