Automatic gearbox - JF403E (Description): Description and operation

DESCRIPTION

This automatic transmission incorporates a three element torque converter with an electronically controlled lock-up, four forward speeds and reverse. It is mounted in-line with the engine.

The transmission contains two shafts, the input and output which each carry sets of helical planetary gears.

In addition to Park ’P’, Reverse ’R’ and Neutral ’N’ positions, there is Drive ’D’ position, giving 1-2-3-4 upshifts and 4-3-2-1 downshifts, and an ’S’ position, with the upshifts occurring at higher road speeds for improved acceleration.

With ’D’ selected, a ’Snow’ mode is also provided, with the transmission starting from rest in second gear to give a smoother take-up of drive on slippery or loose road surfaces.

The gear shifts and converter lock-up mechanism are controlled by an ECU, and five solenoid valves which are located within the main valve body.

Selector lever

The selector lever button beneath the front edge of the selector lever must be depressed before ’P’ or ’R’ can be selected. The reverse light and inhibitor switch assembly is situated on the gearbox. Adjacent to the selector lever is the ’S’ switch and ’Snow’ switch.

Selector positions

’P’ PARK

No drive with mechanical lock on transmission. Select only when vehicle is stationary. Engine start.

’R’REVERSE

Select only when vehicle is stationary. Reverse lights on. No engine start.

’N’ NEUTRAL

No drive Engine start.

’D’ DRIVE

Use for normal driving 1-2-3-4 automatic upshifts and 4-3-2-1 automatic downshifts. No engine start.

’2’ SECOND GEAR

This position limits the transmission to 1-2 automatic upshifts and 2-1 automatic downshifts. Useful for decending hills when maximum engine braking is required. No engine start.

’3’ THIRD GEAR

This position limits the transmission to 1-2-3 automatic upshifts and 3-2-1 automatic down shifts. Useful for driving in congested traffic or town driving. No engine start.

’S’ SPORTS MODE

Available when ’D’ is selected and useful for sports driving or hill climbing this position provides extended gear changes. Upchanges occur at higher speeds. No engine start.

SNOW MODE

Available when ’D’ is selected, the transmission starting from rest in second gear to give a smoother take-up of drive on slippery or loose road surfaces. ’Snow’ mode will override ’Sports’ mode. ’Sports’ mode will resume automatically when when ’Snow’ mode is de-selected.

Torque converter

The torque converter is a three element type incorporating a lock-up clutch which locks the turbine to the impeller in ’D’ range and ’Sport’ and ’Snow’, modes depending upon the vehicle speed and throttle opening.