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Driveline shunt occurs when a vehicle gives an abrupt jolt while coming on or off overrun or freewheel. It is caused when the gearbox or other transmission linkages do not immediately relay changes in engine output to changes in wheel speed. There is a very brief delay before the backlash is taken up in a sudden, abrupt manner.
There are four scenarios where a shunt may occur:
It can occur due to slack within automatic gearboxes, but it can also occur from slack in the other driveline linkages especially where the drive-line is long due to the engine being the opposite end of the vehicle from the driven wheels. Due to the latter it can therefore occur in vehicles with a manual transmission. It has been known to occur even in very new and very high-end vehicles. With experience, most drivers simply allow for it and execute these torque transitions smoothly with finer control of the accelerator. Over time it is expected that engine management systems will increasingly do this on our behalf.
Driveline shunt should not be confused with engine surge in automatic vehicle transmissions where an engine "searches" for its idle speed whilst at very low road speeds, and causes unexpected surges in acceleration. This is a different phenomenon which can be mitigated by an experienced driver using left foot braking for such very low speed maneuvering. [ citation needed ]
A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts. In these devices, one shaft is typically attached to an engine and other to power unit, while the other shaft provides output power for work. Typically the motions involved are rotary, but linear clutches also exist.
Double-clutching is a method of shifting gears used primarily for vehicles with an unsynchronized manual transmission, such as commercial trucks and specialty vehicles. While double clutching is not necessary in a vehicle that has a synchronized manual transmission, the technique can be advantageous for smoothly upshifting in order to accelerate and, when done correctly, it prevents wear on the synchronizers which normally equalize transmission input and output speeds to allow downshifting.
An automatic transmission is a multi-speed transmission used in motor vehicles that does not require any driver input to change forward gears under normal driving conditions. It typically includes a transmission, axle, and differential in one integrated assembly, thus technically becoming a transaxle.
A torque converter is a type of fluid coupling that transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects the power source to the load. It is usually located between the engine's flexplate and the transmission. The equivalent location in a manual transmission would be the mechanical clutch.
Overdrive is the operation of an automobile cruising at sustained speed with reduced engine revolutions per minute (RPM), leading to better fuel consumption, lower noise, and lower wear. The term is ambiguous. The most fundamental meaning is that of an overall gear ratio between engine and wheels, such that the car is over-geared, and cannot reach its potential top speed, i.e. the car could travel faster if it were in a lower gear, with the engine turning at higher RPM.
A transmission is a machine in a power transmission system, which provides controlled application of power. Often the term 5-speed transmission refers simply to the gearbox, that uses gears and gear trains to provide speed and torque block conversions from a rotating power source to another device.
A manual transmission is a multi-speed motor vehicle transmission system, where gear changes require the driver to manually select the gears by operating a gear stick and clutch.
Semi-automatic transmission denotes a multi-speed motor vehicle transmission where part of its operation is automated, but the driver's input is still required to launch the vehicle from a standstill and to manually change gears. Most semi-automatic transmissions used in cars and motorcycles are based on conventional manual transmissions or a sequential manual transmission, but use an automatic clutch system. However, some semi-automatic transmissions have also been based on standard hydraulic automatic transmissions, with, or incorporating a fluid coupling or torque converter, and a planetary gearset.
Engine braking occurs when the retarding forces within an engine are used to slow down a motor vehicle, as opposed to using additional external braking mechanisms such as friction brakes or magnetic brakes.
Hydramatic is an automatic transmission developed by both General Motors' Cadillac and Oldsmobile divisions. Introduced in 1939 for the 1940 model year vehicles, the Hydramatic was the first mass-produced fully-automatic transmission developed for passenger automobile use.
Dynaflow was the trademarked name for a type of automatic transmission developed and built by General Motors Buick Motor Division from late 1947 to mid-1963. The Dynaflow, which was introduced for the 1948 model year only as an option on Roadmaster models, received some severe early testing in the M18 Hellcat tank destroyer, which were built in Buick's Flint Assembly plant during World War II. It was also used in the 1951 Le Sabre concept car.
A direct-shift gearbox is an electronically-controlled, dual-clutch, multiple-shaft, automatic gearbox, in either a transaxle or traditional transmission layout, with automated clutch operation, and with fully-automatic or semi-manual gear selection. The first dual-clutch transmissions were derived from Porsche in-house development for the Porsche 962 in the 1980s.
A preselector gearbox is a type of manual transmission mostly used on passenger cars and racing cars in the 1930s, in buses from 1940-1960 and in armoured vehicles from the 1930s to the 1970s. The defining characteristic of a preselector gearbox is that the gear shift lever allowed the driver to "pre-select" the next gear, usually with the transmission remaining in the current gear until the driver pressed the "gear change pedal" at the desired time.
Hewland is a British engineering company, founded in 1957 by Mike Hewland, which specialises in racing-car gearboxes. Hewland currently employ 130 people at their Maidenhead facility and have diversified into a variety of markets being particularly successful in electric vehicle transmission supply.
A transmission control unit (TCU), also known as a transmission control module (TCM), or a gearbox control unit (GCU), is a type of automotive ECU that is used to control electronic automatic transmissions. Similar systems are used in conjunction with various semi-automatic transmissions, purely for clutch automation and actuation. A TCU in a modern automatic transmission generally uses sensors from the vehicle, as well as data provided by the engine control unit (ECU), to calculate how and when to change gears in the vehicle for optimum performance, fuel economy and shift quality.
A gear stick, gear lever, gearshift or shifter, more formally known as a transmission lever, is a metal lever attached to the transmission of an automobile. The term gear stick mostly refers to the shift lever of a manual transmission, while in an automatic transmission, a similar lever is known as a gear selector. A gear stick will normally be used to change gear whilst depressing the clutch pedal with the left foot to disengage the engine from the drivetrain and wheels. Automatic transmission vehicles, including hydraulic automatic transmissions, automated manual and older semi-automatic transmissions, like VW Autostick, and those with continuously variable transmissions, do not require a physical clutch pedal.
The Turboglide is a Chevrolet constant torque, continuously variable automatic transmission first offered as an option on Chevrolet V8 passenger cars for 1957. It consisted of a concurrently-geared planetary gearbox with a 'switch pitch' dual-pitch torque converter stator. It had a die-cast aluminum transmission case, like Packard's Ultramatic of 1956, and was often ordered with the Rochester Ramjet Fuel Injection system on the 283 V8. The Turboglide cost about $50 more than the Powerglide 2-speed automatic, and was available in all V8-powered 1957-1961 Chevrolet models except the Corvette.
A Multimode Manual Transmission is a type of automated manual transmission offered by Toyota. It uses a traditional manual gearbox with a computer-controlled hydraulic clutch. Multimode Manual Transmission is available in the Aygo, Yaris, Corolla, Corolla Verso, Mark X and Auris in Europe, and should not be confused with Multimode Automatic Transmission, which is offered in the North American market by Toyota.
The drivetrain, also frequently spelled as drive train, or sometimes drive-train, is the group of components of a motor vehicle that deliver power to the driving wheels. This excludes the engine or motor that generates the power. In contrast, the powertrain is considered to include both the engine and/or motor(s), as well as the drivetrain.
Car controls are the components in automobiles and other powered road vehicles, such as trucks and buses, used for driving and parking.
