General Information on the Automatic Transmission

On vehicles with 4A-FE 1.6 L and 3S-FE 2 L engines, a 4-speed automatic transmission may be installed.

The transmission includes a torque converter, planetary gear set, friction discs and hydraulically applied clutches and brakes, and an electronic control system operating together with the engine management system.

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Torque from the engine crankshaft is transmitted to the transmission through the torque converter, which is a type of fluid coupling. The torque converter acts as a clutch and can automatically change torque depending on engine load and vehicle speed. The torque converter operates only when the vehicle starts moving and during gear changes. At all other times it is locked to the engine to reduce losses caused by relative slip and to save fuel.

The planetary gear set provides four forward gears and one reverse gear, depending on which elements inside the automatic transmission are connected or held. Elements are connected or held by hydraulically controlled clutches and brakes. The transmission oil pump supplies fluid at the required pressure to control the friction elements.

The driver can control the transmission using the selector lever and two switches, each with two positions. The selector lever has several positions: D (Drive), 2, L (Low), P (Park), N (Neutral), R (Reverse). In D range the automatic transmission shifts automatically through gears 1 to 4 depending on driving conditions and driver inputs. This is the normal, most frequently used control mode. In this mode the kick-down function also operates, which selects a lower gear when the accelerator pedal is pressed fully.

In range 2 the transmission operates in the same way but shifts only within first and second gears. In range L the transmission operates only in first gear. This range is useful when driving down steep grades, on winding roads and in other situations where driving at limited speed is required. The automatic transmission control system has two shift programs (NORM and PWR) which the driver can select using a two-position switch. In NORM mode, the shift points are selected by the control system for maximum fuel economy. In PWR mode, shifts occur at higher engine speeds, which provides fuller use of engine power and, as a result, faster acceleration.

Another two-position switch enables or disables overdrive mode, i.e. use of the top gear. When the switch is in the ON position, the transmission operates as a four-speed unit, which saves fuel when driving at high speed. Setting the switch to OFF makes the transmission operate as a three-speed unit, and the control system cannot engage top gear. Note that when driving with a cold engine, the control system will not engage 4th gear regardless of the switch position, ON or OFF.

The transmission is controlled by an electronic system shared with the engine. The control system receives signals from sensors that monitor the operation of all engine and transmission systems. Based on this information, the control system selects the optimal shift points according to the driving conditions and the driver's control inputs.

In addition to control functions, the electronic system also performs diagnostic functions, monitoring the condition of the engine and transmission components. When a malfunction occurs, the system alerts the driver by flashing the warning lamp on the instrument panel. In addition, the control system stores trouble codes, which can be read in diagnostic mode and used to determine the nature and location of the malfunction.

Because the automatic transmission is very complex, its repair must be performed at a service station equipped with the appropriate special equipment. However, simple transmission maintenance operations and the correction of minor malfunctions can be performed by the owner.