Note: 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» (ISBN 5-89744-069-7).
The models described in this manual are fitted with an AF17 4-speed automatic transmission.
Note: When modifying engines, it is possible to install other transmission models.
automatic transmission (AT) consists of a torque converter (rotation converter), planetary assembly and hydraulically controlled clutches (clutches) and brake bands. The operation of the transmission is controlled by an electronic module through electrically controlled valves. AT can operate in one of three modes: normal, sport and winter - the order of switching on and the purpose of the modes are described in detail in Chapter «Controls and methods of operation», Section 25.
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 creates the pressure of the working fluid necessary to activate the clutches and brake bands. The driver operates AT by means of the selector lever established on a floor of the car. Control methods are described in detail in Chapter «Controls and methods of operation».
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. In this chapter, only the procedures for diagnosing general transmission failures, its current maintenance, individual adjustments, removal and installation are considered.
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. However, doing the removal and installation yourself will help to a large extent to reduce costs (first make sure that the transmission really needs refurbishment).
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