Land Rover Discovery: Automatic Transmission  Transaxle / Component Description

The transmission comprises the main casing which houses all of the transmission components. The torque converter is located in a separate converter housing, bolted to the main casing.

ZF 9HP48 Cut-Away View

ZF 9HP48 Sectional View

1. Fluid pan
2. Valve block
3. Planetary gear set 4
4. Planetary gear set 3
5. Planetary gear set 2
6. Planetary gear set 1
7. Dog clutch A
8. Spur pinion
9. Park interlock gear
10. Multiplate clutch 'B'
11. Multiplate brake 'C'
12. Multiplate brake 'D'
13. Left splined output shaft (connection to halfshaft)
14. Right splined output shaft (connection to Power Transfer Unit (PTU))
15. Right splined output shaft (connection to halfshaft)
16. Differential
17. Automatic Transmission Fluid (ATF) pump
18. Multiplate clutch 'E'
19. Dog clutch 'F'
20. Input shaft
21. Torsional damper
22. Torque converter stator
23. Torque converter lock-up clutch
24. Torque converter turbine
25. Torque converter assembly
26. Torque converter impeller

The main casing retains the ATF (automatic transmission fluid) at the bottom. A drain plug is located in the main casing. The oil level is checked by removal of a level plug, with the engine running and the transmission fluid at a temperature of between 37 to 45ºC (99 to 113ºF). The level is correct when the oil flow becomes a drip from the level plug hole.

The transmission has a fluid cooler which is located at the front of the transmission, adjacent to the fluid pan. The cooler is connected to the transmission casing by two sealed connections. The fluid cooler is connected into the engine cooling system and cools the transmission fluid by heat transfer through the cooler to the engine coolant.

For additional information, refer to: Transmission Cooling (307-02 Transmission/Transaxle Cooling, Description and Operation).

TORQUE CONVERTER

1. Torque Converter fitted to GTDi 2.0L and TD4 2.2L Engines

1. Turbine
2. Impeller
3. Stator
4. Transmission connection
5. One-way clutch
6. Lock-up clutch
7. Engine drive plate attachment studs
8. Torsional damper
9. Torque converter housing

2. Torque Converter fitted to Ingenium I4 2.0L Diesel Engine

1. Turbine
2. Impeller
3. Stator
4. Transmission connection
5. One-way clutch
6. Lock-up clutch
7. Engine drive plate attachment bolts
8. Torsional damper - including pendulum masses

The torque converter is the coupling element between the engine and the transmission and is located in the torque converter housing, on the engine side of the transmission. The driven power from the engine crankshaft is transmitted hydraulically and mechanically through the torque converter to the transmission. The torque converter is connected to the engine by a drive plate.

The torque converter comprises an impeller, a stator and a turbine. The torque converter is a sealed unit with all components located between the converter housing cover and the impeller. The two components are welded together to form a sealed, fluid filled housing. With the impeller welded to the converter housing cover, the impeller is therefore driven at engine crankshaft speed.

The torque converter contains a hydraulically operated lock-up clutch which is controlled by the TCM via a solenoid in the valve block. The solenoid actuates spool valves to control the hydraulic pressure applied to the clutch.

This allows the TCM to provide 3 modes of converter operation; unlocked, partially locked and fully locked.

Automatic Transmission  Transaxle / Description and operationValve Block

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