wszystko o haldex.pdf

Service.

Self-Study Programme 206

Four-Wheel Drive with Haldex Coupling

Design and Function

Volkswagen and Audi have been building per-

manent four-wheel drive systems for almost 15

years. In Volkswagen's system, a viscous cou-

pling distributes input torque to the rear axle; in

Audi's system this job is performed by a Torsen

differential.

The viscous coupling previously used by Volks-

wagen was able to detect slip alone, but not the

cause of it.

The slip-recognising system is activated by a dif-

ference in speeds between the front and rear

axles. Once activated, it distributes input torque

to both axles.

The development of the Haldex coupling is a

giant step forward in modern four-wheel-drive

technology. The Haldex coupling is controllable.

A processor also makes allowance for additional

information during the control process. Slip is no

longer the only decisive factor in the distribution

of drive forces; the car's dynamic state is also a

factor. The processor accesses the ABS wheel

speed sensors and the engine control unit (acce-

lerator pedal signal) via the CAN bus.

This data provides the processor with all the

information it needs on road speed, cornering,

overrun or traction mode, and can respond opti-

mally to any driving situation.

Advantages of the Haldex coupling

- Permanent four-wheel drive with electroni-

cally controlled multi-plate clutch

- Front drive characteristic

- Quick response

- No strain on clutch when parking and man-

oeuvring vehicle

- Compatible with different tyres (e.g. emer-

gency wheel)

- No restrictions on towing with the axle raised

off the ground

- Fully combinable with traction control systems

such as ABS, EDL, TCS, EBD and ESP

SSP 206/001

NEW

Important

Note

The Self-Study Programme

is not a Workshop Manual.

Please always refer to the relevant Service Literature

for all inspection, adjustment and repair instructions.

Table of contents

Four-wheel drive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Haldex coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Mechanicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Hydraulics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Test your knowledge. . . . . . . . . . . . . . . . . . . . . . . . . . . 19

System overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Electrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Driving situations . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

Function diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

Self-diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

Test your knowledge. . . . . . . . . . . . . . . . . . . . . . . . . . .40

Four-wheel drive

The four-wheel drive train

The four-wheel drive train was developed with

the new multi-plate clutch for Group A platform

vehicles with transversely mounted front engines.

The new coupling is a compact module located in

the same position as the viscous coupling in the

previous drive unit.

It is mounted on the rear axle differential and is

driven by the prop shaft.

SSP 206/003

Engine torque is transmitted to the prop shaft

through the manual gearbox, the front axle diffe-

rential and the front axle drive.

The prop shaft is connected to the input shaft of

the Haldex coupling.

In the Haldex coupling, the input shaft is separa-

ted from the output shaft to the rear axle diffe-

rential.

Torque can only be transmitted to the rear axle

differential via the closed plate set of the Haldex

coupling.

SSP 206/002

SSP 206/004

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