An automatic transmission consists of three main blocks: a torque converter, which is attached directly to the engine; the final drive mechanism, which includes the differential assembly; and planetary gearbox with hydraulically controlled multi-plate clutch and band brake. The transmission also houses a rear-mounted pump that is attached to the torque converter impeller, this pump supplies transmission fluid to the planetary gear, hydraulic control and torque converter. The fluid performs a triple function - lubricates moving parts, cools the automatic transmission system, and provides a medium for torque transmission. The main gear lubrication is separate from the transmission lubrication system, unlike in a manual transmission where the main gear is connected to a common lubrication system.
The torque converter is a non-separable unit. It is bolted to the crankshaft drive plate and replaces the clutch used on manual transmission engines.
The gearbox is of a planetary type, with epicyclic gear sets, brakes and clutches controlled by a hydraulically controlled system. The correct gear is selected by a combination of three control signals: from a mechanical valve controlled by a gear shift cable; from a mechanical valve controlled by the fuel control pedal, and from a regulator that controls the hydraulic pressure. The shift cable and selector lever allow the driver to select a particular gear and make automatic steering adjustments if desired. The throttle control determines the correct gear for the desired degree of acceleration, and the governor determines the correct gear based on engine speed.
Due to the need for special testing equipment, the complexity of some parts, and the need for absolute cleanliness, automatic transmission service procedures are limited. The actions that can be performed are described in detail in the following Chapters. Repairing the final drive differential is also not recommended.
The automatic transmission has three forward speeds and one reverse speed selectable by a lever with six positions as follows:
- P Parking
- R Reverse
- N Neutral
- D Main gear
- 2 low gear
- 1 low gear
Early 1990 Coupe models can be fitted with a four-speed automatic transmission.
'P' position
In the parking position, the transmission is mechanically locked. This position should only be selected when the vehicle is absolutely stationary. The select lever must be depressed to engage 'P' and the brake pedal must also be depressed when pulling away from 'P' with the engine running.
'R' position
Reverse can only be engaged when the vehicle is completely stationary and the engine is idling. The selection lever must be depressed when the 'R' position is engaged, and additionally the brake pedal must be depressed when moving from 'P' to 'R'.
'D' position
This position is for normal driving, and once selected, three forward gears will be automatically engaged over the entire speed range from zero to maximum.
Position '2'
With the lever in this position, the lower two gears are selected automatically, but the highest one will not engage. For this reason, position '2' should only be selected when the vehicle speed is below 115 km/h. Position selection '2' uses the result of engine braking and actually speed change can only be done by depressing the throttle pedal.
Position '1'
The position is rarely needed, only on steep ascents or descents. The transmission remains in the lowest gear and therefore the '1' position should only be pulled out when the vehicle speed is below 65 km/h.
Towing Precautions
If the vehicle is being towed, the ignition key must be positioned so that the steering wheel is not locked and the gear selector must be in the 'N' position (neutral). Due to limited lubrication of the transmission when the engine is not running, the vehicle must not be towed more than 50 km, or at speeds greater than 50 km/h, unless the vehicle's front wheels are raised off the road.
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