Land Rover Discovery: Automatic Transmission Transaxle
/ Description and operation
COMPONENT LOCATION
![Automatic Transmission Transaxle / Description and operation](images/books/227/index436(2).jpg)
- Paddle switches - upshift / downshift
- Transmission Control Switch (TCS)
- Transmission Control Module (TCM)
- ZF 9HP48 Automatic transmission
- Automatic Transmission Fluid (ATF) cooler with integrated thermostat
OVERVIEW
The ZF 9HP48 automatic transmission is a 9 speed, electronically controlled
unit manufactured by ZF. The transmission represents the latest in automatic
transmission technology for a transverse, AWD (all-wheel drive) unit. The
transmission features lock-up slip control, 'CommandShift' functions and
automatic and driver selectable modes to give the optimum on and off road
performance.
The automatic transmission is controlled by a TCM (transmission control
module) which contains software to provide operation as a semi-automatic
'CommandShift' transmission. Driver selections for P, R, N, D and S on the
rotary TCS (transmission control switch) are received by the TCM. The TCM
operates solenoid valves and clutches to control transmission gear shifts,
allowing the system to operate as a 'shift by wire' system, with no
mechanical link to the transmission for drive selections.
The TCM allows the transmission to be operated as a conventional
automatic unit by selecting P, R, N, D, S on the TCS. Rotation of the TCS to
the 'S' position puts the transmission into electronic 'Sport' mode.
Operation of the steering wheel mounted + or - paddle switches puts the
transmission into electronic manual 'CommandShift' mode.
For additional information, refer to: External Controls (307-05 Automatic
Transmission/Transaxle External Controls, Description and Operation).
The ZF 9HP48 transmission has the following features:
- Designed to be maintenance free
- Transmission fluid is fill for life
- The torque converter features a controlled slip feature with
electronically
regulated lock-up control on gears 1 to 9
- Planetary gearset with 9 speeds, 4 planetary geartrains, and 6 shift
elements
- Wide transmission ratio spread with small ratio steps
- The first-ever use of interlocking dog clutches in a passenger car
automatic transmission
- Shift programs controlled by the TCM
- TCM has an adaptive capability to ensure efficient gear shift quality
throughout the service life of the transmission
- Diagnostics available from the TCM via the high speed CAN (controller
area network) Powertrain systems bus.
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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-Awa
The valve block is located in a vertical position at the front of the
transmission main casing, behind a sealed cover. The valve block contains a
number of solenoids and spool valves to control the t
Multiplate Drive or Brake Clutch - Typical
Cylinder
Piston
Disk spring
Metal plates
Friction plates
Baffle plate
Pressure equalization chamber
Piston chamber
There are two multiplate drive
SEE MORE:
PRINCIPLES OF OPERATION
For a detailed description of the Power Steering, refer to the relevant
Description and Operation section in the workshop manual. REFER to:
Power Steering (211-02 Power Steering, Description and Operation).
Inspection and verification
CAUTION:
Diagnosis by substitution from a
PRINCIPLES OF OPERATION
For a detailed description of the Tire Pressure Monitoring System, refer to
the relevant Description and Operation section in the workshop manual.
REFER to: (204-04 Wheels and Tires)
Wheels and Tires (Description and Operation),
Tire Pressure Monitoring System LocSync (Descr