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.
A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both. In a more general context, a coupling can also be a mechanical device that serves to connect the ends of adjacent parts or objects. Couplings do not normally allow disconnection of shafts during operation, however there are torque-limiting couplings which can slip or disconnect when some torque limit is exceeded. Selection, installation and maintenance of couplings can lead to reduced maintenance time and maintenance cost.
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.
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 continuously variable transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios. This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. The flexibility of a CVT with suitable control may allow the engine to operate at a constant RPM while the vehicle moves at varying speeds.
Bell housing or bellhousing is a colloquial/slang term for the portion of the transmission that covers the flywheel and the clutch or torque converter of the transmission on vehicles powered by internal combustion engines. This housing is bolted to the engine block and derives its name from the bell-like shape that its internal components necessitate. The starter motor is usually mounted here, and engages with a ring gear on the flywheel. On the opposite end to the engine is usually bolted to the gearbox. The use of different bellhousings on a transmission allows the same transmission to be used on multiple engines in multiple applications. However, on some transmissions, the bellhousing is a nonremovable part of the transmission case. This is particularly true with front wheel drive transmissions, which are much shorter than conventional rear wheel drive transmissions.
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.
A starter ring gear is a part attached to an internal combustion engine that is part of the assembly which transfers the torque from the starter motor to the engine's crankshaft, in order to start the engine. The starter ring gear is usually made from medium carbon steel.
A viscous coupling is a mechanical device which transfers torque and rotation by the medium of a viscous fluid.
Roto Hydramatic was an automatic transmission built by General Motors and used on some Oldsmobile, Pontiac and Holden models from 1961–1965. It was based on the earlier, four-speed Hydramatic, but was more compact, providing only three forward speeds plus a small 8" fluid coupling with a stator inside of the fluid coupling. Oldsmobile, one of the users of this transmission, called the fluid couplings stator the "Accel-A-Rotor." The lightweight, aluminum-cased transmission was sometimes nicknamed the "Slim Jim." HydraMatic Division calls the Roto a four range, three gear HydraMatic. It counts the stator multiplication at 3.50:1 as a first gear, and when road speed and the two coupling halves speed match, it counts the same gear with fluid now passing straight through the stator as 2nd gear at 2.93 to one. Second gear has a ratio of 1.56 and because the fluid coupling is drained for this gear ratio making the front clutch apply makes this a rare automatic that is in FULL mechanical lock-up in second gear. Fourth range the coupling fills releasing the front clutch makes a ratio of 1 to 1. This transmission, like single and dual range, and dual coupling hydramatics also have the feature of split torque in the transmission whereby in fourth or high gear only 40-to 50% depending on transmission, 40% in Roto's case, but because of the design the coupling is only required to carry 40% of the engine torque. The rest is (60%) is in full mechanical connection making these hydramatics the most efficient automatic until the wide spread use of the lock-up torque converter.
A fluid coupling or hydraulic coupling is a hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch. It also has widespread application in marine and industrial machine drives, where variable speed operation and controlled start-up without shock loading of the power transmission system is essential.
Fluid Drive is the trademarked name that Chrysler Corporation assigned to a transmission driveline combination which replaced the flywheel with a hydraulic coupling and performed the same function as a modern torque converter, only without torque multiplication. A conventional clutch and three- or four-speed manual transmission was installed behind the fluid coupling. Fluid drive was used in many military vehicles produced for the US Armed Forces during the Second World War. It was offered for civilian use from 1939 through 1953 in Chryslers, 1940 through 1953 in DeSotos, and from 1941 through 1954 in Dodge models; a semi-automatic system was optional from Chrysler and Desoto from 1941, and for Dodge from 1949.
A magnetic coupling is a coupling that transfers torque from one shaft to another, but using a magnetic field rather than a physical mechanical connection.
Vehicles made by American Motors Corporation (AMC) and Jeep incorporated a variety of transmissions and transfer case systems. This article covers transmissions used in the following vehicle models and years:
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.
Electromagnetic clutches operate electrically but transmit torque mechanically. This is why they used to be referred to as electro-mechanical clutches. Over the years, EM became known as electromagnetic versus electro-mechanical, referring more about their actuation method versus physical operation. Since the clutches started becoming popular over 60 years ago, the variety of applications and clutch designs has increased dramatically, but the basic operation remains the same today.
Splines are ridges or teeth on a drive shaft that matches with grooves in a mating piece and transfer torque to it, maintaining the angular correspondence between them.
Olavi Koskenhovi "O.K." immigrated from Finland in 1921 at age 17 and changed his name to Oliver K. Kelley. In 1940, Kelley became the engineer in charge of Automatic Transmission Development General Motors Corporation.
