Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Automatic Transmission shopping experience:

1. Compare - without doubt the biggest advantage that the Automatic Transmission offers shoppers today is the ability to compare thousands of Automatic Transmission at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.

2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about

3. Testimonials - don't know anybody that has bought a Automatic Transmission? Wrong! If the Automatic Transmission is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.

4. Questions - Got a question about Automatic Transmission then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....

5. Reputation - Never heard of the company selling Automatic Transmission? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Automatic Transmission and build up a picture of their reputation for sales, returns, customer service, delivery etc.

6. Returns - still worried that even after all of the above your Automatic Transmission wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.

7. Feedback - happy with your Automatic Transmission then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.

8. Security - check for the yellow padlock on the Automatic Transmission site before you buy, and the s after http:/ /i.e. https:// = a secure site

9. Contact - got a question about Automatic Transmission, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.

10. Payment - ready to pay for your Automatic Transmission, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.

in a Ford Five Hundred vehicle

An automatic transmission (commonly abbreviated as "AT") is an automobile gearbox that can change gear ratios automatically as the vehicle moves, thus freeing the driver from having to shift gears manual transmission (similar but larger devices are also used for railroad Locomotive#Diesel-hydraulic).

image:torque-converter-cutbox-model.jpg

Most automatic transmissions have a set selection of possible gear ranges, often with a parking pawl feature that will lock the output shaft of the transmission.

However, some simple machines with limited speed ranges and/or fixed engine speeds only use a torque converter to provide a variable gearing of the engine to the wheels. Typical examples include forklift trucks and some modern lawn mowers.

Recently manufacturers have begun to make continuously variable transmissions commonly available (earlier models such as the Subaru Justy did not popularize CVT). These designs can change the ratios over a range rather than between set gear ratios. Even though CVTs have been used for decades in two-wheeled scooters and in a few cars (e.g. Van Doorne's Automobiel Fabriek saloons and the Volvo 340 series that succeeded them, and later the Subaru Justy), the technology has recently gained greater acceptance among manufacturers and customers.

Comparison with manual transmission Most cars sold in the United States since the 1950s have been equipped with an automatic transmission. This has, however, not been the case in Europe. In most Asian markets, automatic transmission became very popular from the 1990s. Automatic transmission provides lower fuel efficiency and power than manual transmission, though the gap is significantly narrowed with modern designs. Automatic transmission is easier for drivers, especially beginners. In some jurisdictions, drivers passing their driving test in an automatic-transmission vehicle will not be driving license to drive a manual transmission vehicle.

Automatic transmission modes Conventionally, in order to select the mode, the driver would have to move a gear shift lever located on the steering column or on the floor next to him/her. In order to select gears/modes the driver must push a button in (called the shift lock button) or pull the handle (only on column mounted shifters) out. Some vehicles (like the Aston Martin DB9) position selector buttons for each mode on the cockpit instead, freeing up space on the central console. Vehicles conforming to US Government standards must have the modes ordered P-R-N-D-L (left to right, top to bottom, or clockwise).

Automatic Transmissions have various modes depending on the model and make of the transmission. Some of the common modes are:

Park (P) – This selection mechanically locks the transmission, restricting the car from moving in any direction. A parking pawl prevents the transmission from moving forward (although wheels, depending on the drive train, can still spin freely), it is recommended to use the hand brake (or emergency brake) because this actually locks the wheels and prevents them from moving, and increases the life of the transmission and the park mechanism. A car should be allowed to come to a complete stop before setting transmission into park to prevent damage. Park is one of only two selections in which the car can be started. In some cars (notably those sold in the US), the driver must have the footbrake depressed before the transmission can be taken out of park. The Park position is omitted on buses/coaches with automatic transmission, which must be placed in neutral with the parking brakes set.

Reverse (R) – This puts the car into the reverse gear, giving the ability for the car to drive backwards. In order for the driver to select reverse they must come to a complete stop, and push the shift lock button in and select reverse. Not coming to a complete stop can cause severe damage to the transmission. Many modern automatic gearboxes have a safety mechanism in place, which does to some extent prevent (but doesn't completely avoid) inadvertently putting the car in reverse when the vehicle is moving. This mechanism usually consists of a moveable physical barrier on either side of the Reverse position, and is electronically linked to the brake pedal, which needs to be pressed in order to allow putting the car in reverse. Some electronic transmissions prevent/delay engagement of reverse gear altogether when the car is moving.

Neutral/No gear (N)– This disconnects the transmission from the wheels so the car can move freely under its own weight. This is the only other selection in which the car can be started.

Drive (D)– This allows the car to move forward and accelerate through a range of gears. The number of gears a transmission has depends on the model, but they can commonly range from 3, 4 (the most common), 5, 6 (found in VW/Audi Direct Shift Gearbox), 7 (found in Mercedes 7G gearbox) and 8 in the new model of Lexus cars. Some cars when put into D will automatically lock the doors or turn on the Daytime Running Lamps.

As well as the above modes, there are also other modes dependant on the manufacturer and model. Some examples include;



Overdrive (mechanics) (, OD, or a boxed D) - This mode is used in some transmissions (including late 1980s Chevrolet) to allow early Computer Controlled Transmissions to engage the Automatic Overdrive; in these transmissions, Drive (D) locks the Automatic Overdrive off, but is identical otherwise. OD in these cars engaged under steady speeds or low acceleration at 45mph (72 kph); it would automatically come on at 65 mph (104 kph) under hard acceleration.

Second (2 or S) – This mode limits the transmission to the first two gears, or more commonly locks the transmission in second gear. This can be used to drive in adverse conditions such as snow and ice, as well as climbing or going down hills in the winter time.

First (1 or L) – This mode locks the transmission in first gear only. It will not accelerate through any gear range. This, like second, can be used during the winter season, or towing.

Hydraulic automatic transmissions The predominant form of automatic transmission is Hydraulic machinery operated, using a fluid coupling or torque converter and a set of epicyclic gearing to provide a range of torque multiplication.

Parts and operation A hydraulic automatic transmission consists of the following parts:

The multitude of parts, along with the complex design of the valve body, originally made hydraulic automatic transmissions much more complicated (and expensive) to build and repair than manual transmissions. In most cars (except US family, luxury, sport-utility vehicle, and minivan models) they have usually been extra-cost options for this reason. Mass manufacturing and decades of improvement have reduced this cost gap.

History and improvements Oldsmobile's 1940 models featured Hydra-Matic drive, the first mass-production fully automatic transmissions. Initially an Olds exclusive, Hydra-Matic had a fluid coupling (not a torque converter) and three planetary gearsets providing four speeds plus reverse. Hydra-Matic was subsequently adopted by Cadillac and Pontiac, and was sold to various other automakers, including Bentley Motors Limited, Hudson Motor Car, Kaiser Motors, Nash Motors, and Rolls-Royce Limited. From 1950 to 1954 Lincoln (automobile) cars were also available with GM Hydra-Matic. Mercedes-Benz subsequently devised a four-speed fluid coupling transmission that was similar in principle to Hydra-Matic, but did not share the same design.

The first torque converter automatic, Buick's Dynaflow, was introduced for the 1948 model year. It was followed by Packard's Ultramatic in mid-1949 and Chevrolet's Powerglide for the 1950 model year. Each of these transmissions had only two forward speeds, relying on the torque converter for additional gear reduction. In the early 1950s Borg-Warner developed a series of three-speed torque converter automatics for American Motors Corporation, Ford Motor Company, Studebaker, and several other manufacturers in the US and other countries. Chrysler Corporation was late in developing its own true automatic, introducing the two-speed torque converter PowerFlite in 1953 and the three-speed TorqueFlite in 1956.

By the late 1960s most of the fluid-coupling four-speeds and two-speed transmissions had disappeared in favor of three-speed units with torque converters. Also around this time, whale oil was removed from automatic transmission fluid. Almost Burned By the early 1980s these were being supplemented and eventually replaced by overdrive (mechanics)-equipped transmissions providing four or more forward speeds. Many transmissions also adopted the lock-up torque converter (a mechanical clutch locking the torque converter impeller and turbine together to eliminate slip at cruising speed) to improve fuel economy.

As the electronic control units became more and more capable, even more of the valve body's functionality was offloaded to them. These transmissions, introduced in the late 1980s and early 1990s, remove almost all of the control logic from the valve body, and place it in into the engine computer. (Some manufacturers use a separate computer dedicated to the transmission but sharing information with the engine management computer.) In this case, solenoids turned on and off by the computer control shift patterns and gear ratios, rather than the spring-loaded valves in the valve body. This allows for more precise control of shift points, shift quality, lower shift times, and (on some newer cars) semi-automatic control, where the driver tells the computer when to shift. The result is an impressive combination of efficiency and smoothness. Some computers even identify the driver's style and adapt to best suit it.

ZF Friedrichshafen AG and BMW were responsible for introducing the first six-speed (the ZF 6HP26 transmission in the 2002 BMW BMW E65 BMW 7-Series). Mercedes-Benz's 7G-Tronic was the first seven-speed in 2003, with Toyota Motor Company introducing an 8-speed in 2007 on the Lexus LS 460.

Automatic transmission models Some of the best known automatic transmission families include:

Automatic transmission families are usually based on Ravigneaux, Lepelletier, or Simpson Epicyclic gearingsets. Each uses some arrangement of one or two central sun gears, and a ring gear, with differing arrangements of planet gears that surround the sun and mesh with the ring. An exception to this is the Hondamatic line from Honda, which uses sliding gears on parallel axes like a manual transmission without any planetary gearsets. Although the Honda is quite different from all other automatics, it is also quite different from an automated manual transmission.

Continuously variable transmissions A different type of automatic transmission is the continuously variable transmission or CVT, which can smoothly alter its gear ratio by varying the diameter of a pair of belt (mechanical) or roller chain-linked pulleys, wheels or cone (mechanical)s. Some continuously variable transmissions use a hydrostatic drive consisting of a variable displacement pump and a hydraulic motor to transmit power without gears. CVT designs are usually as fuel efficient as manual transmissions in city driving, but early designs lose efficiency as engine speed increases.

A slightly different approach to CVT is the concept of toroidal CVT or Continuously variable transmission#infinitely variable transmission (from infinitely variable transmission). These concepts provide zero and reverse gear ratios.

Some current hybrid vehicles, notably those of Toyota, Lexus and Ford Motor Company, have an "electronically-controlled CVT" (E-CVT). In this system, the transmission has fixed gears, but the ratio of wheel-speed to engine-speed can be continuously varied by controlling the speed of the third input to a Differential_(mechanics) using an electric motor-Electrical generator.

Manually controlled automatic transmissions Most automatic transmissions offer the driver a certain amount of manual control over the transmission's shifts (beyond the obvious selection of forward, reverse, or neutral). Those controls take several forms:



Some automatic transmissions modified or designed specifically for drag racing may also incorporate a transmission brake, or "trans-brake," as part of a manual valve body. Activated by electrical solenoid control, a trans-brake simultaneously engages the first and reverse gears, locking the transmission and preventing the input shaft from turning. This allows the driver of the car to raise the engine rpm against the resistance of the torque converter, then launch the car by simply releasing the trans-brake switch.

See also

External links

References

in a Ford Five Hundred vehicle

An automatic transmission (commonly abbreviated as "AT") is an automobile gearbox that can change gear ratios automatically as the vehicle moves, thus freeing the driver from having to shift gears manual transmission (similar but larger devices are also used for railroad Locomotive#Diesel-hydraulic).

image:torque-converter-cutbox-model.jpg

Most automatic transmissions have a set selection of possible gear ranges, often with a parking pawl feature that will lock the output shaft of the transmission.

However, some simple machines with limited speed ranges and/or fixed engine speeds only use a torque converter to provide a variable gearing of the engine to the wheels. Typical examples include forklift trucks and some modern lawn mowers.

Recently manufacturers have begun to make continuously variable transmissions commonly available (earlier models such as the Subaru Justy did not popularize CVT). These designs can change the ratios over a range rather than between set gear ratios. Even though CVTs have been used for decades in two-wheeled scooters and in a few cars (e.g. Van Doorne's Automobiel Fabriek saloons and the Volvo 340 series that succeeded them, and later the Subaru Justy), the technology has recently gained greater acceptance among manufacturers and customers.

Comparison with manual transmission Most cars sold in the United States since the 1950s have been equipped with an automatic transmission. This has, however, not been the case in Europe. In most Asian markets, automatic transmission became very popular from the 1990s. Automatic transmission provides lower fuel efficiency and power than manual transmission, though the gap is significantly narrowed with modern designs. Automatic transmission is easier for drivers, especially beginners. In some jurisdictions, drivers passing their driving test in an automatic-transmission vehicle will not be driving license to drive a manual transmission vehicle.

Automatic transmission modes Conventionally, in order to select the mode, the driver would have to move a gear shift lever located on the steering column or on the floor next to him/her. In order to select gears/modes the driver must push a button in (called the shift lock button) or pull the handle (only on column mounted shifters) out. Some vehicles (like the Aston Martin DB9) position selector buttons for each mode on the cockpit instead, freeing up space on the central console. Vehicles conforming to US Government standards must have the modes ordered P-R-N-D-L (left to right, top to bottom, or clockwise).

Automatic Transmissions have various modes depending on the model and make of the transmission. Some of the common modes are:

Park (P) – This selection mechanically locks the transmission, restricting the car from moving in any direction. A parking pawl prevents the transmission from moving forward (although wheels, depending on the drive train, can still spin freely), it is recommended to use the hand brake (or emergency brake) because this actually locks the wheels and prevents them from moving, and increases the life of the transmission and the park mechanism. A car should be allowed to come to a complete stop before setting transmission into park to prevent damage. Park is one of only two selections in which the car can be started. In some cars (notably those sold in the US), the driver must have the footbrake depressed before the transmission can be taken out of park. The Park position is omitted on buses/coaches with automatic transmission, which must be placed in neutral with the parking brakes set.

Reverse (R) – This puts the car into the reverse gear, giving the ability for the car to drive backwards. In order for the driver to select reverse they must come to a complete stop, and push the shift lock button in and select reverse. Not coming to a complete stop can cause severe damage to the transmission. Many modern automatic gearboxes have a safety mechanism in place, which does to some extent prevent (but doesn't completely avoid) inadvertently putting the car in reverse when the vehicle is moving. This mechanism usually consists of a moveable physical barrier on either side of the Reverse position, and is electronically linked to the brake pedal, which needs to be pressed in order to allow putting the car in reverse. Some electronic transmissions prevent/delay engagement of reverse gear altogether when the car is moving.

Neutral/No gear (N)– This disconnects the transmission from the wheels so the car can move freely under its own weight. This is the only other selection in which the car can be started.

Drive (D)– This allows the car to move forward and accelerate through a range of gears. The number of gears a transmission has depends on the model, but they can commonly range from 3, 4 (the most common), 5, 6 (found in VW/Audi Direct Shift Gearbox), 7 (found in Mercedes 7G gearbox) and 8 in the new model of Lexus cars. Some cars when put into D will automatically lock the doors or turn on the Daytime Running Lamps.

As well as the above modes, there are also other modes dependant on the manufacturer and model. Some examples include;



Overdrive (mechanics) (, OD, or a boxed D) - This mode is used in some transmissions (including late 1980s Chevrolet) to allow early Computer Controlled Transmissions to engage the Automatic Overdrive; in these transmissions, Drive (D) locks the Automatic Overdrive off, but is identical otherwise. OD in these cars engaged under steady speeds or low acceleration at 45mph (72 kph); it would automatically come on at 65 mph (104 kph) under hard acceleration.

Second (2 or S) – This mode limits the transmission to the first two gears, or more commonly locks the transmission in second gear. This can be used to drive in adverse conditions such as snow and ice, as well as climbing or going down hills in the winter time.

First (1 or L) – This mode locks the transmission in first gear only. It will not accelerate through any gear range. This, like second, can be used during the winter season, or towing.

Hydraulic automatic transmissions The predominant form of automatic transmission is Hydraulic machinery operated, using a fluid coupling or torque converter and a set of epicyclic gearing to provide a range of torque multiplication.

Parts and operation A hydraulic automatic transmission consists of the following parts:

The multitude of parts, along with the complex design of the valve body, originally made hydraulic automatic transmissions much more complicated (and expensive) to build and repair than manual transmissions. In most cars (except US family, luxury, sport-utility vehicle, and minivan models) they have usually been extra-cost options for this reason. Mass manufacturing and decades of improvement have reduced this cost gap.

History and improvements Oldsmobile's 1940 models featured Hydra-Matic drive, the first mass-production fully automatic transmissions. Initially an Olds exclusive, Hydra-Matic had a fluid coupling (not a torque converter) and three planetary gearsets providing four speeds plus reverse. Hydra-Matic was subsequently adopted by Cadillac and Pontiac, and was sold to various other automakers, including Bentley Motors Limited, Hudson Motor Car, Kaiser Motors, Nash Motors, and Rolls-Royce Limited. From 1950 to 1954 Lincoln (automobile) cars were also available with GM Hydra-Matic. Mercedes-Benz subsequently devised a four-speed fluid coupling transmission that was similar in principle to Hydra-Matic, but did not share the same design.

The first torque converter automatic, Buick's Dynaflow, was introduced for the 1948 model year. It was followed by Packard's Ultramatic in mid-1949 and Chevrolet's Powerglide for the 1950 model year. Each of these transmissions had only two forward speeds, relying on the torque converter for additional gear reduction. In the early 1950s Borg-Warner developed a series of three-speed torque converter automatics for American Motors Corporation, Ford Motor Company, Studebaker, and several other manufacturers in the US and other countries. Chrysler Corporation was late in developing its own true automatic, introducing the two-speed torque converter PowerFlite in 1953 and the three-speed TorqueFlite in 1956.

By the late 1960s most of the fluid-coupling four-speeds and two-speed transmissions had disappeared in favor of three-speed units with torque converters. Also around this time, whale oil was removed from automatic transmission fluid. Almost Burned By the early 1980s these were being supplemented and eventually replaced by overdrive (mechanics)-equipped transmissions providing four or more forward speeds. Many transmissions also adopted the lock-up torque converter (a mechanical clutch locking the torque converter impeller and turbine together to eliminate slip at cruising speed) to improve fuel economy.

As the electronic control units became more and more capable, even more of the valve body's functionality was offloaded to them. These transmissions, introduced in the late 1980s and early 1990s, remove almost all of the control logic from the valve body, and place it in into the engine computer. (Some manufacturers use a separate computer dedicated to the transmission but sharing information with the engine management computer.) In this case, solenoids turned on and off by the computer control shift patterns and gear ratios, rather than the spring-loaded valves in the valve body. This allows for more precise control of shift points, shift quality, lower shift times, and (on some newer cars) semi-automatic control, where the driver tells the computer when to shift. The result is an impressive combination of efficiency and smoothness. Some computers even identify the driver's style and adapt to best suit it.

ZF Friedrichshafen AG and BMW were responsible for introducing the first six-speed (the ZF 6HP26 transmission in the 2002 BMW BMW E65 BMW 7-Series). Mercedes-Benz's 7G-Tronic was the first seven-speed in 2003, with Toyota Motor Company introducing an 8-speed in 2007 on the Lexus LS 460.

Automatic transmission models Some of the best known automatic transmission families include:

Automatic transmission families are usually based on Ravigneaux, Lepelletier, or Simpson Epicyclic gearingsets. Each uses some arrangement of one or two central sun gears, and a ring gear, with differing arrangements of planet gears that surround the sun and mesh with the ring. An exception to this is the Hondamatic line from Honda, which uses sliding gears on parallel axes like a manual transmission without any planetary gearsets. Although the Honda is quite different from all other automatics, it is also quite different from an automated manual transmission.

Continuously variable transmissions A different type of automatic transmission is the continuously variable transmission or CVT, which can smoothly alter its gear ratio by varying the diameter of a pair of belt (mechanical) or roller chain-linked pulleys, wheels or cone (mechanical)s. Some continuously variable transmissions use a hydrostatic drive consisting of a variable displacement pump and a hydraulic motor to transmit power without gears. CVT designs are usually as fuel efficient as manual transmissions in city driving, but early designs lose efficiency as engine speed increases.

A slightly different approach to CVT is the concept of toroidal CVT or Continuously variable transmission#infinitely variable transmission (from infinitely variable transmission). These concepts provide zero and reverse gear ratios.

Some current hybrid vehicles, notably those of Toyota, Lexus and Ford Motor Company, have an "electronically-controlled CVT" (E-CVT). In this system, the transmission has fixed gears, but the ratio of wheel-speed to engine-speed can be continuously varied by controlling the speed of the third input to a Differential_(mechanics) using an electric motor-Electrical generator.

Manually controlled automatic transmissions Most automatic transmissions offer the driver a certain amount of manual control over the transmission's shifts (beyond the obvious selection of forward, reverse, or neutral). Those controls take several forms:



Some automatic transmissions modified or designed specifically for drag racing may also incorporate a transmission brake, or "trans-brake," as part of a manual valve body. Activated by electrical solenoid control, a trans-brake simultaneously engages the first and reverse gears, locking the transmission and preventing the input shaft from turning. This allows the driver of the car to raise the engine rpm against the resistance of the torque converter, then launch the car by simply releasing the trans-brake switch.

See also

External links

References



automatic transmission
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Automatic transmission - Wikipedia, the free encyclopedia
An automatic transmission (commonly abbreviated as "AT") is an automobile gearbox that can change gear ratios automatically as the vehicle moves, freeing the driver from having to ...

Federation of Automatic Transmission Engineers FATE automatic gearbox ...
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Amsoil Synthetic Automatic Transmission Fluid
AMSOIL Performance Oils Ltd are the Sole UK Importers for AMSOIL synthetic ATF. BUY Amsoil synthetics ONLINE.

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we rebuild /repair /service all types of automatic transmissions and automatic gearboxes and CVT gearboxes for cars, forklift trucks, commercal vehicles, glider winches.

Chester Automatic Transmission Centre
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Information about safer driving in cars fitted with automatic transmission. ... Why choose an 'Automatic' If you are reading this in the USA you might be thinking "Why choose a ...

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Automatic transmission – for crawling in the slow lane or emergencies in the fast lane. Emergency vehicles, such as fire tenders, have road-going performance and handling ...

Automatic Choice, The European Transmission Parts Warehouse
Specialists in the repair and rebuild of automatic transmission units. Located in Trafford Park Village.

 

Automatic Transmission



 
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