TCM FB-8 Series, Service Manual

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(4) When the pump fails to operate normally
If the pump fails to supply pressure oil to the orbitrol, the orbitrol can serve as an emergency
manual steering device. Even if the orbitrol does not receive pressure oil from the pump, you can
rotate the spool by turning the steering wheel. However, when the spool turns 8°, it hits against
the cross pin, which in turn turns the rotor through the drive shaft. This way, the metering device
of the orbitrol works as a hand pump to send oil to the steering cylinder. At this time, the check
valve provided between the return port and the suction port opens to allow the oil to flow from the
cylinder to the suction side, making it possible to steer the truck manually.
6A.1.4 POWER CYLINDER
The power cylinder is attached to the steering axle and operated by oil from the orbitrol. The
cylinder body is secured to the axle, with both ends of the piston rod connected to the knuckles
with joints.
The cylinder cap has a bushing, an oil seal, and a dust seal, and is assembled on the cylinder
with two bolts.
A
Fig. 6A.11 Power Cylinder
BUSHING
BUSHING
BOLT
CAP
PACKING
PISTON ROD
“O”-RING
BUSHING
PACKING
DUST SEAL
Tightening torque:
27.7 to 41.5 N-m
{28.3 to 42.3 kgf-m}
[20.43 to 30.6 lbf-ft]
22 mm [0.87 in.]: 1 to 1.8 ton
15 mm [0.59 in.]: 2.0 to 3.5 ton
View looking from A
6A. STEERING SYSTEM (ORBITROL type)