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Land Rover Range Rover System Description & Operation Manuals

Drive Clutches > < Valve Block and Solenoid Valves
Page 150
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AUTOMATIC TRANSMISSION – ZF 5HP24

DESCRIPTION AND OPERATION 44-2-17

Solenoid EPRS1 supplies a lower control pressure as the signal amperage increases. The EPRS1 solenoid is a 
normally closed regulating flow solenoid valve and regulates the main line pressure. The solenoid is used for adaptive 
pressure control. The EAT ECU operates the solenoid using PWM signals. The EAT ECU monitors engine load and 
clutch slip and varies the solenoid duty cycle accordingly.

Solenoids EPRS2, 3 and 5 supply a higher control pressure as the signal amperage increases. The solenoids are 
normally open solenoids regulating flow solenoid valves. The solenoids are used to regulate the supply of fluid 
pressure for clutch application during overlap up and down shifts of gears 2–3, 3–4 and 4–5. The EAT ECU operates 
the solenoids using a PWM earth proportional to the required increasing or decreasing clutch pressures.

The resistance of the coil winding for solenoid EPRS1 is between 5.4 to 6.4

 at 20

°

C (68

°

F). The resistance of the 

coil windings for solenoids EPRS2, 3, 4 and 5 is between 5.9 and 6.9

 at 20

°

C (68

°

F).

Shift Control Solenoids

Coil winding
Valve

Spring

Three shift control Solenoid Valves (SV) are located in the valve block. The solenoids are controlled by the EAT ECU 
and convert electrical signals into hydraulic control signals to control clutch application.

The shift control solenoids SV1, 2 and 3 are normally closed, on/off solenoids which are controlled by the EAT ECU 
switching the solenoid to earth. The EAT ECU also supplies the power to solenoids. The EAT ECU energises the 
solenoids in a programmed sequence for clutch application for gear ratio changes and shift control.

The resistance of the coil winding for solenoids SV1, 2 and 3 is between 26 to 30.4

 at 20

°

C (68

°

F).

Dampers
There are six dampers located in the valve block. Four of the dampers are used to regulate and dampen the regulated 
pressure supplied via the pressure regulating solenoid valves. The two remaining dampers are used for operation of 
clutches 'A' and 'C' and providing damping of the fluid pressure during shift changes. All of the dampers are load 
dependent through modulation of the damper against its return spring pressure.

The dampers comprise a piston, a housing bore and a spring. The piston is subject to the pressure applied by the 
spring. The bore has a connecting port to the function to which it applies. Fluid pressure applied to the applicable 
component (i.e. a clutch) is also subjected to the full area of the piston, which moves against the opposing force 
applied by the spring. The movement of the piston creates an action similar to a shock absorber, momentarily delaying 
the build up of pressure in the circuit. This results in a more gradual application of clutches improving shift quality.

M44 1826

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Drive Clutches > < Valve Block and Solenoid Valves