Land Rover Discovery: Four-Wheel Drive Systems - Vehicles With- Active Driveline / Description and Operation

COMPONENT LOCATION - VEHICLES WITH ACTIVE DRIVE LINE

NOTE:

Automatic transmission shown, manual transmission similar

1. Power Transfer Unit (PTU)
2. Driveshaft
3. Rear Drive Unit (RDU)
4. Hydraulic lines

OVERVIEW

Vehicles with Active Driveline connect to the transmission in the same way as vehicles without Active Driveline. The Active Driveline system differs with the fitment of an enhanced Power Transfer Unit (PTU) which can disconnect the drive to the driveshaft and a twin clutch Rear Drive Unit (RDU) which replaces the active on-demand coupling of vehicles fitted without Active Driveline.

The Active Driveline system comprises an enhanced PTU, a three-piece driveshaft and a twin clutch RDU. The system is controlled by an All Wheel Drive Control Module (AWDCM) and the PTU and RDU are hydraulically operated by a Rear Drive Unit (RDU) pump and All Wheel Drive (AWD) valve block.

The Active Driveline system is able to disconnect the entire driveline using two points of disconnection; one at the PTU input and a second at the RDU drive shafts, allowing FWD (front wheel drive) only, providing maximum fuel economy. A control strategy continuously monitors key vehicle and environmental parameters. If the requirements for AWD (all-wheel drive) are met, the system reconnects the AWD system via a synchroniser in the PTU and by closing the clutches in the RDU.

No driver intervention is required with Active Driveline. If the driver has selected a Terrain Response Special Programme, the system will automatically engage and/or maintain AWD. System operation is displayed to the driver via a graphical display in the Touch Screen (TS).

The PTU is located at the rear of the engine and is attached directly to the right side of the transmission casing. A bracket on the PTU attaches the unit to the engine cylinder block.

When required, the PTU transfers the output from the transmission and distributes it to the rear wheels via a three-piece driveshaft to the RDU. The front halfshafts are driven from the transmission front differential, not the PTU.

The PTU, linked to the transmission's final drive differential, contains a synchroniser and brake to disconnect the AWD upstream of the PTU hypoid gears.

The Rear Drive Unit (RDU) is attached to the rear subframe.

The RDU drives each rear halfshaft and wheel via an independent wet multiplate clutch. These clutches can disconnect the AWD system at the halfshaft interface to the RDU. The PTU synchronizer and RDU are controlled by a dedicated All Wheel Drive Control Module (AWDCM) designed to constantly monitor vehicle dynamics, disconnecting during steady-state driving speeds above 22mph and automatically reconnecting (within 300 milliseconds) when required.

In addition to the disconnect function the RDU also acts as an electric rear differential combining drive vectoring and limited slip differential technology for active torque biasing.

DESCRIPTION

• Power Transfer Unit (PTU)/ Description
• Rear Drive Unit (RDU)/ Description
• All Wheel Drive Control Module (AWDCM) / Description
• Power Transfer Unit (PTU) / Operation
• Rear Drive Unit (RDU)/ Operation
• Active Driveline System

Clutch System Bleeding (G1353044) / General ProceduresPower Transfer Unit (PTU)/ Description

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