General information
The models covered in this manual can be equipped with one of two types of 4-speed automatic transmissions (with overdrive): A343F and A440F, and since 2002, issue. - 5-speed AT. All transmissions are equipped with a lock-up rotation converter (torque converter). The converter provides direct coupling between the engine and driving wheels of the car.
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 AT failures, its current maintenance, basic adjustments, removal and installation are considered.
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 reconditioning).
Attention! Towing a car with a failed AT must be carried out at a speed of no more than 50 km / h and at a distance of no more than 80 km!
Operating principle
Assembly of a typical AT
1 - Torque converter with a lockup clutch; 2 - Increasing planetary gear; 3 - Gearbox; 4 - Transfer box; 5 - Valve assembly of the gear shift control system; 6 - Valve assembly of the transfer box switching control system
The automatic transmission consists of a torque converter with a lock-up clutch, a step-up planetary gear set, a gearbox, a transfer case and a control system that includes hydraulic and electronic parts (refer to illustration above).
The planetary gear assembly consists of two planetary gear sets. The transfer case includes a planetary gear set with friction controls (lockup clutch and brake). The operation of the entire transmission is controlled by an electronic control unit. Switching of high-speed modes is made by means of the selector lever established in inside of the car. The selector is connected to the valve assembly by means of a cable, and with its help it is possible to set the range of gears used. In addition to the selector in the cabin, several switches are provided to set special modes of operation of the transmission.
To prevent breakdowns of the AT when the speed range is incorrectly selected, for example, moving from «D» V «R» there is a lock on the selector lever, «dangerous» switching can only be carried out when the lock button is pressed. The selector lever can be set to one of six fixed positions: «R», «R», «D», «N», «2» and «L», the purpose of each of which is discussed below.
Position «R»
Selected when parking the car. In this position, all controls are turned off in the transmission, and its output shaft is blocked, it is impossible to move the car. Move selector to position «R» only after the vehicle has come to a complete stop.
Attention! Translation of the selector into position «R» while driving can lead to transmission failure!
Position «R»
Reverse. Move selector to position «R» possible only after the vehicle has come to a complete stop.
Attention! Engaging reverse gear while the vehicle is moving can damage the transmission!
Position «N»
Neutral position. In the box, all controls are turned off, which ensures the absence of a rigid kinematic connection between its drive and driven shafts. In this case, the output shaft blocking mechanism is disabled, i.e. the car can move freely. It is not recommended to shift the transmission to the position «N» when coasting.
Attention! Never turn off the ignition when driving downhill!
Position «D»
Basic driving mode. Provides automatic shifting from first to fourth gear. Recommended for driving under normal conditions.
Position «2»
Driving is allowed only in first and second gears. It is recommended to use, for example, when driving on winding mountain roads. Switching to third and fourth gears is prohibited. In this range, the engine braking mode is effectively used.
Position «L»
Driving is allowed only in first gear. This range allows maximum implementation of the engine braking mode. It is recommended when driving on steep descents, climbs and off-road.
Mode «OD»
Permission to use the fourth, overdrive, gear is carried out using a special button «OD». If the button is in the recessed state and the lever is set to the position «D», then upshifting is allowed. Otherwise, the inclusion of the fourth (boosting) transmission is prohibited. The state of the control system in this case is determined by the control lamp «O/D OFF». If overdrive is enabled, the indicator is off; if it is disabled, it is on. The mode is used when driving at a constant speed on straight sections of the motorway. The use of the O/D mode in urban areas should be avoided, especially during the winter season when engine braking becomes vital. Also, do not turn on the overdrive mode when the car is fully loaded.
Special programs
On vehicles with AT, there are two modes of gear shift control: «economical» (NORMAL) And «sports» (POWER). The choice is made by means of a special switch mounted in the center console of the car.
Economy mode (NORMAL)
In this mode, there is a minimum fuel consumption. Gear shifts occur in the middle of the corresponding engine ranges, the character of the car's movement is calm, smooth.
Sports mode (POWER)
When this mode is enabled, the control lamp lights up on the panel of priors «ECT POWER». In this mode, the maximum engine power is taken off, the box is switched at the upper limit of the corresponding engine speed ranges. The acceleration of the car is greatly increased, fuel consumption, respectively, increases.
Planetary gearbox
The planetary gearbox consists of three planetary gear sets, three lockup clutches, four brakes and three freewheels.
Power from the engine through the torque converter is transmitted to the input shaft of the planetary gearbox.
Gear shifting is accomplished by applying a specific combination of brakes and freewheels, which changes the speed of the output shaft.
Another planetary gear set, two locking clutches and one brake contains a transfer case.
The device of the hydraulic part of the control system
Transmission
The hydraulic part of the control system consists of an oil pump, valve assembly, solenoid valves, clutches and brakes, as well as channels connecting the listed elements. The fluid pressure generated by the pump is used to control the friction elements of the transmission, feed the torque converter and lubricate. The valve assembly contains three switching solenoid valves. With their help, the electronic unit controls the gear shift and torque converter lockup.
Transfer case
The hydraulic part of the transfer box control system includes: valve box, solenoid valve No. 4, brake (AT 4), two locking clutches (NW, C4), as well as channels connecting the listed elements (refer to accompanying illustration). The purpose of the box is to control the planetary series, which can be carried out either manually or automatically by an electronic unit.
The assembly of the transfer case is shown in the illustration below.
Transfer case assembly
Electrical part of the control system
The electrical part controls gear shifting in the gearbox and transfer case, as well as the torque converter lock-up clutch. It consists of three parts: vehicle speed sensors (VSS),throttle position sensor (TPS) and other information sensors that monitor transmission status parameters and transmit ECM data (electronic control unit); ECM, which, based on the analysis of data coming to it, determines the shift points in the gearbox and transfer case, and also controls the torque converter lock-up clutch; and the executive part, consisting of four solenoid valves.