Ford Kuga

 Service Manual

Rear Drive Axle/Differential » Rear Drive Axle and Differential (System Operation and Component Description)
Haldex clutch

General overview

Haldex clutches of the 3rd and 4th generations are used in the Ford Kuga.

The development of the third generation Haldex clutch represents a big step forward in modern all-wheel technology. The Haldex clutch is electro-hydraulically controlled. Additional information is taken into consideration during control tasks via the all-wheel drive control unit.

Slip alone is no longer decisive for the distribution of the propulsive forces; the vehicle's driving dynamics are also taken into consideration. The control unit accesses the driving-related data via the data bus. With this data, the control unit has all the essential information about speed, cornering, coasting or traction operation, and can optimally react to every driving situation.

Compared with the previous generation, the 4th generation Haldex clutches operate with higher pressure and achieve shorter response times when distributing the drive forces.

Advantages of the Haldex clutch:

• Permanent all-wheel drive with electronically-controlled multi-plate clutch
• Fast response
• No straining when parking and manoeuvring
• Compatible with different tyres (e.g. emergency spare wheel)
• Fully combinable with driving dynamic control systems

The driveshaft is connected to the input shaft of the Haldex clutch. Within the Haldex clutch, the input shaft is separated from the output shaft to the rear axle differential by means of a multi-plate clutch. Torque is only transmitted to the rear axle differential when the plate assembly of the Haldex clutch is closed.

The multi-plate clutch is electro-hydraulically controlled via the all-wheel drive control unit. For ecological driving, the torque to the rear axle is reduced to a minimum up to a throttle position of approx. 50%. A prerequisite for this is that there is no difference in speed in the Haldex clutch between the input and output shafts.

Operation

Within the Haldex clutch is a plate assembly and a so-called ring piston pump with a pump plunger and a working piston.

Fluid supply is started if there is a speed difference between the input and output shafts.

This fluid pressure is transmitted to the working piston and in this way the plate assembly is compressed.

General Information

Driving situations

Haldex clutch

Design of the 3rd generation Haldex clutch

Design of the multi-plate clutch

All-wheel drive control unit

Electric feed pump

Pressure control - 3rd generation Haldex clutch

Base pressure

Increased base pressure (preload)

Pressure build-up

Design of the 4th generation Haldex clutch

Pressure control - 4th generation Haldex clutch