Land Rover Discovery: Automatic Transmission  Transaxle / Description and operation

COMPONENT LOCATION

1. Paddle switches - upshift / downshift
2. Transmission Control Switch (TCS)
3. Transmission Control Module (TCM)
4. ZF 9HP48 Automatic transmission
5. 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.

• Automatic Transmission  Transaxle / Component Description
• Valve Block
• Drive Clutches
• Planetary Gear Trains
• Park Lock
• Instrument Cluster
• Transmission Fault Status
• Engine Speed and Torque Monitoring

External Controls / Diagnosis and TestingAutomatic Transmission  Transaxle / Component Description

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