Automatic transmission — general description (Peugeot 406)

Models with 2.0 liter petrol engines can be equipped with a computer that controls a four-speed automatic transmission consisting of a torque converter, gear train and hydraulically controlled clutch and brakes.

The gearbox is controlled by an electronic control device (ECU), which receives signals from various sensors related to the operating conditions of the gearbox. Based on this data, the ECU can set the optimum vehicle speeds according to the driving style.

Torque from the engine to the gearbox is transmitted through a torque converter, which functions as a fluid clutch and acts as an automatic clutch, also providing torque transfer during acceleration.

The gear drive provides forward movement in one of the 4 gears or reverse movement. The gear train components are controlled by brakes and clutches which are actuated hydraulically. A pump located in the gearbox provides the necessary hydraulic pressure to operate the brake and clutch.

The gearbox is controlled by a selector lever with 7 positions. Position "D" provides automatic gear selection from 4 forward gears. The automatic downshift mechanism downshifts when the accelerator pedal is fully depressed. This mode should be used when maximum vehicle acceleration is required. Downshifting is similar to other transmission functions and is controlled by the ECU. If the selector lever is in position "3", the car will move only in the first three gears, and in the position "2" - only in the first two gears, etc. Lower gears are desirable when engine braking, when driving downhill, or to prevent unwanted high gear selection on winding roads.

In addition, three drive programs, controlled by a switch to the left of the selector lever, provide additional driver control over the gear according to road conditions. Pregnant "Normal" the gearbox operates in normal automatic mode. In mode "Sport" gear shifting occurs at higher engine speeds. In mode "Snow" in selector lever position "D" the vehicle starts in second gear.

Due to the complexity of the automatic transmission, any repair must be done at a Peugeot station.