Automatic transmission fluid

Automatic transmission fluid (ATF), also known as transmission fluid or tranny fluid for short, is the fluid used in vehicles with self shifting or automatic transmissions. It is typically coloured red or green to distinguish it from motor oil and other fluids in the vehicle. The fluid is optimized for the special requirements of a transmission, such as valve operation, brake band friction and the torque converter as well as gear lubrication. ATF is also used as a hydraulic fluid in some power assisted steering systems, as a lubricant in some 4WD transfer cases, and in some modern manual transmissions. Automatic transmission fluid Modern use Modern ATF typically contains a wide variety of chemical compounds intended to provide the required properties of a particular ATF specification. Most ATFs contain some combination of additives that improve lubricating qualities, such as anti-wear additives, rust and corrosion inhibitors, detergents, dispersants and surfactants (which protect and clean metal surfaces); kinematic viscosity and viscosity index improvers and modifiers, seal swell additives and agents (which extend the rotational speed range and temperature range of the additives' application); anti-foam additives and anti-oxidation compounds to inhibit oxidation and "boil-off" (which extends the life of the additives' application); cold-flow improvers, high-temperature thickeners, gasket conditioners, pour point depressant and petroleum dye. All ATFs contain friction modifiers, except for those ATFs specified for some Ford transmissions and the John Deere J-21A specification; the Ford ESP (or ESW) - M2C-33 F specification Type F ATF (Ford-O-Matic) and Ford ESP (or ESW) - M2C-33 G specification Type G ATF (1980s Ford Europe and Japan) specifically excludes the addition of friction modifiers. According to the same oil distributor, the M2C-33 G specification requires fluids which provide improved shear resistance and oxidation protection, better low-temperature fluidity, better EP (extreme pressure) properties and additional seal tests over and above M2C-33 F quality fluids. There are many specifications for ATF, such as the DEXRON and MERCON series, and the vehicle manufacturer will identify the ATF specification appropriate for each vehicle. The vehicle's owner's manual will typically list the ATF specification(s) that are recommended by the manufacturer. Automatic transmission fluids have many performance-enhancing chemicals added to the fluid to meet the demands of each transmission. Some ATF specifications are open to competing brands, such as the common DEXRON specification, where different manufacturers use different chemicals to meet the same performance specification. These products are sold under license from the OEM responsible for establishing the specification. Some vehicle manufacturers will require "genuine" or Original Equipment Manufacturer (OEM) ATF. Most ATF formulations are open 3rd party licensing, and certification by the automobile manufacturer. Each manufacturer has specific ATF requirements. Incorrect transmission...

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Transmission brake

A transmission brake or driveline parking brake is an inboard vehicle brake that is applied to the drivetrain rather than to the wheels. Historically, some early cars used transmission brakes as the normal driving brake and often had wheel brakes on only one axle, if that. In current vehicles, these brakes are now rare. They are found in some makes, notably Land Rover, usually for light off-road vehicles. Simple transmission brakes could be found in large vehicles too, such as the 16 inch single disc parking brake used in the M19 Tank Transporter of World War II. The transmission brake is provided solely as a parking brake or handbrake. Normal wheel brakes are still provided for use when driving, drum brakes originally, now almost always disc brakes. Driver's manuals usually caution against using the transmission brake when driving, as it is neither powerful enough nor robust enough and so will not work effectively and may even be damaged by trying to stop a moving vehicle. Land Rover 90 rolling chassis, with drivetrain painted yellow. The transmission brake is the yellow drum, to the right rear of the transfer box. Transmission brakes use drum brakes, rather than disc brakes, as they are intended as a static parking brake, rather than a high performance dynamic brake. Drum brakes allow simpler adjustment with cable-actuated hand lever mechanisms. The brake is mounted to the rear output shaft of the transfer box. As the transmission brake is mounted inboard of the final drive and its reduction gearing, the brake rotates relatively faster, but with less torque, than a wheel brake. The apparently undersized transmission brake thus has more holding ability than its small size might suggest, but is less suitable for driving loads. The braking forces would also be passed through the final drive and axle drive shafts, with possible risk of overloading them. One advantage of a transmission brake is that it locks the entire drivetrain, including all four wheels of a four wheel drive vehicle. However any differential action, either within an axle or front-to-back on an all wheel drive (permanent 4×4) vehicle can still allow movement. For this reason a transmission brake is convenient as a parking brake, but should not be relied upon if a mechanic is to be working beneath the vehicle and wheel chocks should be used instead. A second advantage is that they remove the need to provide cable connections to the wheel brakes, on off-road vehicles where such may be prone to damage. Automatic transmissions Pawl transmission brake, inside an automatic transmission A form of transmission brake is commonly fitted to automatic transmissions. These brakes...

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