1999 LAND ROVER DISCOVERY automatic transmission

AUTOMATIC GEARBOX - ZF4HP22 - 24
44-16 DESCRIPTION AND OPERATION
Warning lamps
Warning lamps and selector lever position indication
1Transmission temperature warning lamp (red)
2Gear selector lever position indication3Sport mode warning lamp (green)
4Manual mode warning lamp (green)
Illumination for each warning lamp is provided by a non serviceable LED.

AUTOMATIC GEARBOX - ZF4HP22 - 24
DESCRIPTION AND OPERATION 44-17
Operation
Refer to illustration.

+ AUTOMATIC GEARBOX - ZF4HP22 - 24, DESCRIPTION AND OPERATION, Control schematic.
When the ignition is switched on, a bulb check is performed on the transmission temperature warning lamp and the
mode warning lamps by the instrument pack and the EAT ECU respectively. The warning lamps are illuminated for
approximately 3 seconds and then extinguished.
The gear position switch outputs are monitored by the BCU and the EAT ECU. The BCU outputs gear position signals
to illuminate the position indicators each side of the gear selector lever and on the odometer LCD in the instrument
pack.
In D, 3, 2, and 1, the EAT ECU outputs control signals to the gearbox to select the required gear.
In D, all forward gears are available for selection by the EAT ECU. In 3, 2 and 1, a corresponding limit is imposed on
the highest gear available for selection. When R is selected, reverse gear only engages if the vehicle is stationary or
moving at 5 mph (8 km/h) or less. When R is deselected, reverse gear only disengages if the vehicle is moving at 4
mph (6 km/h) or less.
Selector lever interlock (where fitted)
The interlock solenoid on the selector lever is de-energised unless the foot brake is applied while the ignition is on.
While de-energised, the interlock solenoid allows the selector lever to move through the range unless P is selected.
On entering the P position, the interlock solenoid engages a latch which locks the selector lever. When the ignition is
on and the foot brake is applied, the BCU energises the interlock solenoid, which disengages the latch and allows the
selector lever to be moved out of P.
Economy, sport and manual modes
During the power-up procedure after the ignition is switched on, the EAT ECU defaults to an economy mode. Pressing
the mode switch causes the EAT ECU to change between the economy mode and the sport or the manual mode,
depending on the range selected on the transfer box:
lIf the transfer box is in high range, the EAT ECU changes to the sport mode and illuminates the sport mode
warning lamp in the instrument pack. In the sport mode the gearbox is more responsive to accelerator pedal
movement. Downshifts occur earlier and upshifts occur later.
lIf the transfer box is in low range, the EAT ECU changes to the manual mode and illuminates the manual mode
warning lamp in the instrument pack. Kickdown is disabled and the EAT ECU maintains the gearbox in the gear
selected on the selector lever (D = 4th gear) to give improved off road performance. Downshifts occur only to
prevent the engine stalling. From a standing start, the vehicle pulls away in 1st gear and, if a higher gear is
selected, upshifts almost immediately to the selected gear (shifts of more than one gear can occur).
After a second press of the mode switch the EAT ECU reverts to the economy mode, for the range selected on the
transfer box, and extinguishes the related mode warning lamp in the instrument pack.
Shift control
To provide the different driving characteristics for each mode of operation, the EAT ECU incorporates different shift
maps of throttle position/engine speed. Base shift points are derived from the appropriate shift map. When a shift is
required, the EAT ECU sends a request to the ECM for a reduction in engine torque, in order to produce a smoother
shift. The percentage of torque reduction requested varies according to the operating conditions at the time of the
request. When the EAT ECU receives confirmation of the torque reduction from the ECM, it then signals the shift
solenoid valves in the gearbox to produce the shift. To further improve shift quality, the EAT ECU also signals the
pressure regulating solenoid valve to modulate the hydraulic pressure and so control the rate of engagement and
disengagement of the brake clutches.
With time, the components in a gearbox wear and the duration of the gear shifts tends to increase, which has an
adverse effect on the brake clutches. To counteract this, the EAT ECU applies a pressure adaptation to each shift.
To calculate the adaptations, the EAT ECU monitors the pressure modulation used, and time taken, for each shift. If
a subsequent shift of the same type, in terms of throttle position and engine speed, has a longer duration, the EAT
ECU stores an adaptation for that type of shift in a volatile memory. The adaptation is then included in future pressure
calculations for that type of shift, to restore shift duration to the nominal.

AUTOMATIC GEARBOX - ZF4HP22 - 24
44-20 DESCRIPTION AND OPERATION
P1613
(1)* Solenoid valves
power supply relay,
sticking open or short
circuitLimp home mode in low and high ranges. Shift
pressure to maximum, harsh gear shifts/
engagement.On On
P1705
(39)Transmission high/low
range, implausible
inputNo apparent effect On Off
P1810
(12, 13)Sport/Manual warning
lamp circuit faultLamp fails bulb check or is permanently
illuminated. No effect on gearbox operation.On Off
P1841
(16)* CAN bus fault Maintains current gear in low range, limp
home mode in high range. Shift pressure to
maximum, harsh gear shifts/engagement.On On
P1842
(15)* CAN level monitoring Maintains current gear in low range, limp
home mode in range. Shift pressure to
maximum, harsh gear shifts/engagement.On On
P1843
(17)* CAN time-out
monitoringMaintains current gear in low range, limp
home mode in high range. Shift pressure to
maximum, harsh gear shifts/engagement.On On
P1884
(11)* CAN message:
Engine friction invalidNo apparent effect. On Off
P1884
(18)* CAN message:
Throttle position invalidSubstitute throttle angle of 50% adopted. No
kickdown. Operates in economy modes only.On On
P1884
(19)CAN message: Engine
temperature invalidSubstitute engine temperature derived from
other inputs. No apparent effect.On Off
P1884
(20)CAN message: Road
speed invalidNo apparent effect On Off
P1884
(33, 34)* CAN message:
Engine torque invalidSubstitute engine torque of derived from other
inputs. May affect shift quality.On Off
P1884
(35)* CAN message:
Engine speed invalidMaintains current gear in low range, limp
home mode in high range. Shift pressure to
maximum, harsh gear shifts/engagement.On On
P1884
(37)CAN message: Engine
air intake temperature
invalidNo apparent effect. On Off
P1844
(38)Altitude shift control
invalidNo reduced torque compensation, possible
reduction in performance/ driveability at
altitude or high ambient temperatures.On Off
* = Emissions (OBD II) relevant
†On = MIL illuminates immediately (in all other faults, MIL On = illuminates in the 2nd consecutive drive cycle if
fault still present)Fault code,
OBD II
(TestBook)Fault description Effect Warning lamp
illumination
MIL Sport/
Manual

AUTOMATIC GEARBOX - ZF4HP22 - 24
REPAIRS 44-37
Torque converter and oil seal
$% 44.17.07
Remove
1.Remove automatic gearbox.
l

+ AUTOMATIC GEARBOX -
ZF4HP22 - 24, REPAIRS, Gearbox -
convertor and transfer gearbox - Diesel.
l

+ AUTOMATIC GEARBOX -
ZF4HP22 - 24, REPAIRS, Gearbox -
convertor and transfer gearbox - V8.
2.Remove retaining strap from torque convertor.
3.Fit tool LRT-44-010 to torque converter and
remove torque converter from gearbox.
4.Remove tool LRT-44-010 from converter.
5.Remove oil seal from converter housing. Refit
1.Clean oil seal running surfaces.
2.Lubricate oil seal with transmission fluid.
3.Fit new seal into converter housing using tool
LRT-44-001.
4.Fit tool LRT-44-010 to torque converter.
5.Align oil pump drive and fit torque converter to
gearbox.
6.Remove tool LRT-44-010 from torque
converter.
7.Fit torque converter retaining strap.
8.Fit automatic gearbox.
l

+ AUTOMATIC GEARBOX -
ZF4HP22 - 24, REPAIRS, Gearbox -
convertor and transfer gearbox - Diesel.
l

+ AUTOMATIC GEARBOX -
ZF4HP22 - 24, REPAIRS, Gearbox -
convertor and transfer gearbox - V8.

AUTOMATIC GEARBOX - ZF4HP22 - 24
44-42 REPAIRS
Refit
1.Clean intermediate plate and mating faces with
a lint free cloth.
2.Position intermediate plate to converter
housing, fit bolts and tighten evenly to 46 Nm
(34 lbf.ft)
3.Fit new sealing washers to M14 Allen plugs, fit
plugs and tighten to 40 Nm (30 lbf.ft).
4.Fit new sealing washers to M20 plugs, fit plugs
and tighten to 50 Nm (37 lbf.ft).
5.Fit oil cooler adaptors and tighten to 42 Nm (30
lbf.ft)
6.Clean pump housing and mating face on
intermediate plate with lint free cloth.
7.Lubricate new 'O' ring with transmission fluid
and fit to pump housing.
8.Position pump locating dowel into intermediate
plate.
9.Align pump to dowel and position in
intermediate plate.
10.Fit bolts and tighten in a diagonal sequence to
10 Nm (7 lbf.ft)
11.Position LRT-44-003/1 into pump and check
that the pump rotors turn freely.
12.Fit intermediate plate gasket.

+ AUTOMATIC GEARBOX - ZF4HP22
- 24, REPAIRS, Gasket - intermediate plate.
M44 1342
LRT-44-003/1

AUTOMATIC GEARBOX - ZF4HP22 - 24
REPAIRS 44-43
Pump - fluid
$% 44.32.01
Remove
1.Remove intermediate plate gasket.

+ AUTOMATIC GEARBOX - ZF4HP22
- 24, REPAIRS, Gasket - intermediate plate.
2.Remove 8 bolts securing fluid pump to
intermediate plate and carefully remove pump
from intermediate plate.
3.Note position and remove pump locating dowel.
4.Remove and discard 'O' ring from pump
housing.Refit
1.Clean pump housing and mating face on
intermediate plate with lint free cloth.
2.Lubricate new 'O' ring with transmission fluid
and fit to pump housing.
3.Position pump locating dowel into intermediate
plate.
4.Align fluid pump to dowel and position in
intermediate plate.
5.Fit bolts and tighten in a diagonal sequence to
10 Nm (7 lbf.ft)
6.Position LRT-44-003/1 into pump and check
that the pump rotors turn freely.
7.Fit intermediate plate gasket.

+ AUTOMATIC GEARBOX - ZF4HP22
- 24, REPAIRS, Gasket - intermediate plate.
M44 1336
M44 1341
M44 1342
LRT-44-003/1

AUTOMATIC GEARBOX - ZF4HP22 - 24
44-44 REPAIRS
Seal - rear extension housing
$% 44.20.18
Remove
1.Remove transfer box

+ TRANSFER BOX - LT230SE,
REPAIRS, Transfer box - Diesel.

+ TRANSFER BOX - LT230SE,
REPAIRS, Transfer box - V8.
2.Drain automatic gearbox oil.

+ MAINTENANCE, PROCEDURES,
Automatic gearbox.
3.Remove rear extension housing oil seal from
gearbox. Refit
1.Clean oil seal recess in gearbox and running
surface on input shaft.
2.Lubricate oil seal running surface with
transmission oil.
3.Using tool LRT-44-001 fit oil seal to extension
housing.
4.Fit transfer box

+ TRANSFER BOX - LT230SE,
REPAIRS, Transfer box - Diesel.

+ TRANSFER BOX - LT230SE,
REPAIRS, Transfer box - V8.
5.Fill automatic gearbox with oil.

+ MAINTENANCE, PROCEDURES,
Automatic gearbox.

AUTOMATIC GEARBOX - ZF4HP22 - 24
44-58 REPAIRS
Electronic control unit - automatic
transmission
$% 44.15.46
Remove
1.Release fixings and remove battery cover.
2.Disconnect battery earth lead.
3.Remove 3 screws and trim clip securing lower
trim casing to LH front seat.
4.Remove 3 nuts securing speaker power
amplifier bracket to the body.
5.Disconnect multiplug from automatic
transmission ECU located on underside of
amplifier mounting bracket.6.Remove 2 nuts securing ECU to mounting
bracket and remove ECU.
Refit
1.Position ECU to mounting bracket and secure
with nuts.
2.Connect multiplug to ECU.
3.Position speaker power amplifier mounting
bracket to body and secure with nuts.
4.Position lower trim casing to seat and secure
with screws and trim clip.
5.Connect battery earth lead.
6.Fit battery cover and secure fixings.