A detailed description of the principles of operation and designs used on most modern cars of automatic transmissions is devoted to Manual No. 179 of the publishing house «ARUS».
The location of the AT and its related components in the engine compartment of the car (bottom view)
1 - Amplifier of the power unit
2 - Subframe
3 — a cable of a drive of a gear change
4 — the Holder of a cable of switching
5 — a cover of a cable of a drive of switching
4-speed automatic transmission (AT) consists of a torque converter (rotation converter), planetary assemblies and hydraulically controlled clutches and brake bands. The transmission is controlled by the ECM through electrically controlled valves. AT has three driving modes: normal (economical), sports and winter.
Normal (economical) mode designed for normal driving style, when upshifting occurs at relatively low engine speeds, corresponding to the minimum fuel consumption mode. Switch to sports mode It is carried out using a button located on the selector lever and leads to a delay in upshifts of the transmission, which leads to an increase in the dynamic characteristics of the car, but is accompanied by a slight increase in fuel consumption. The control lamp warns about the inclusion of the sport mode «SPORT» (see chapter Manual). To enable winter regime function, it is intended to switch located on the center console, - when this mode is activated, the car starts from a place from the third gear, which significantly improves the quality of the grip of the treads with slippery road surfaces.
torque converter (rotation converter) transfers torque from the engine to the gearbox. Due to the fact that the transmission of rotation is carried out hydraulically (through the transmission fluid - ATF), starting off the car and shifting gears are very smooth. In addition, the torque converter provides dynamic torque adjustments during acceleration.
The AT planetary mechanism provides a choice of four forward and one reverse gears. The gear ratio of a planetary gearbox is determined by which of its elements are locked and which rotate freely. The blocking and release of the elements of the planetary assemblies in the AT is carried out using clutches and brake bands activated by commands from the control module. The hydraulic pump placed inside the transmission housing is the pressure of the working fluid necessary to activate the clutches and brake bands.
The driver controls the AT by means of a vehicle mounted on the floor and having seven positions of the selector lever. Position «D» (Drive) provides the ability to shift the transmission to any of the four forward gears, while the kickdown function provides automatic downshifting when the gas pedal is pressed all the way down (in order to increase the gear ratio, which provides the car with increased dynamic characteristics, necessary, for example, when overtaking). IN position «1» the front shifts of the transmission are completely locked and the car can only move in first gear. Choice provisions «2» And «3» provides transmission shifts between the first two / three gears, providing the ability to perform engine braking in difficult road conditions (e.g. when driving in mountainous terrain). It should be remembered that AT downshifting can only occur after an adequate reduction in engine speed. Position «R» (Reverse) corresponds to the choice of reverse gear, position «N» (Neutral) - neutral and position «R» - parking.
Due to the inclusion in the trigger circuit of a special sensor-switch (start enable switch) starting the engine becomes possible only in the positions «R» And «N» selector lever, the same sensor-switch provides operation of the reverse lights when the lever is moved to the position «R».
Due to the complexity of the AT design, the lack of free sale of replaceable internal components, and the need to use special equipment, the compilers of this Guide do not recommend car owners to overhaul the transmission on their own. This Chapter covers only the procedures for diagnosing common transmission failures, its current maintenance, adjustments, removal and installation.
Sometimes, in the event of a serious breakdown, it is wiser and easier to replace the transmission than to spend time and money on rebuilding a failed assembly. Regardless of the chosen method of introducing a failed AT into operation, the independent implementation of its removal and installation will help to significantly reduce costs (first make sure that the transmission really needs refurbishment).
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