TRANSMISSION AND TORQUE CONVERTER 5540F/YB5515 SERVICE MANUAL
7-18 Published 10-21-2010, Control# 198-04
Hydraulic 2/4-Wheel Drive Unit (Spring ON/
Pressure OFF)
2wd Cannot Be Engaged
In normal operation the 2/4-wheel drive clutch is spring
loaded and therefore engaged to give 4-wheel drive. The
clutch must be pressurised to give 2-wheel drive. Before
starting the more detailed fault finding procedures - eliminate
the obvious:
1. Check that the transmission oil level is correct.
2. Check that the fuse for the 2/4WD circuit is intact.
3. Check that the 4-wheel drive external pipework is not
damaged.
4. Check that all the electrical connections are clean and
secure.
5. Check that the mainline pressure is correct, see Low
Mainline Pressure.
6. Check that the pump flow rate is correct.
If the fault is not rectified after eliminating the obvious, check
the following
4WD CANNOT BE ENGAGED
No pressure is required to engage 4WD (spring loaded).
Check that the front wheel drive train is intact (i.e. propshaft
and axle). Also check that the solenoid spool is not sticking
(in the 2WD position). Finally check the 2/4-wheel drive
switch and relays
Possible Cause Remedy
7. Low mainline pressure
(Minimum pressure required to disengage 2/4WD
clutch is 8.6 bar; 125 psi).
7. Identify if the fault is related to the 2/4WD disconnect:
a. Disconnect the external pipework to the 2/4WD
clutch. Cap and plug open orifices.
b. Check the mainline pressure - if the pressure is
correct, the fault must be within the 2/4WD (see step
8). If the reading is still low check the transmission in
the normal manner.
8. Low mainline pressure (due to 2/4WD clutch):
a. 2/4WD solenoid spool sticking.
b. 2/4WD solenoid permanently energized.
c. 2/4WD solenoid spool O-ring failed.
d. Clutch shaft sealing rings leaking.
e. Excessive clutch shaft end float.
f. Clutch piston O-ring failed.
8. Rectify fault:
a. Strip, clean and re-assemble solenoid valve, renew
valve if required.
b. Check the 2/4WD relay and select switch, replace as
necessary.
c. Renew O-ring.
d. Renew clutch shaft sealing rings.
e. Rectify fault, renew parts as required, reset end float
(should not exceed 0.03 mm; 0.001 in)
f. Replace clutch piston O-ring.
9. Defective 2/4WD clutch:
a. Worn pressure (counter) plate
b. Worn actuating sleeve.
c. Incorrect clutch pack end float
9. Rectify fault:
a. Inspect pressure (counter) plate, renew as required.
b. Measure length of actuating sleeve and renew as
required, sleeve length should be 2.390 in (60.70
mm).
c. Measure clutch pack end float, should be 0.030 -
0.059 in (0.75 -1.5 mm). Correct as required
Reference Only
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