control handle. The adjustment nut will compensate
for wear on the lock or kingpin.
Lockguard
(Fig. 10.4)
The Holland lockguard is a device that prevents a
false lockup, and is used on all models. The Lock-
guard is a spring-tensioned, smooth-surfaced tongue
that the kingpin passes over and depresses when
entering the lock mechanism. The Lockguard will
prevent the locks from engaging before the kingpin
fully enters the locks. If the kingpin enters the fifth
wheel incorrectly and does not depress the tongue,
the locks are unable to close.
Fifth Wheel Locking Operation
Locking the Fifth Wheel Mechanism
NOTICE
Before attempting to lock or unlock the fifth
wheel lock mechanism of a sliding type fifth
wheel, the slide release plungers must be in the
locked position. This prevents the sliding mem-
ber from moving rapidly to the far forward or
rearward position, which could damage the fifth
wheel or kingpin.
1.
Chock the front and rear of the trailer tires to
prevent the trailer from moving.
WARNING
Keep the fifth wheel plate lubricated to prevent
binding between the tractor and trailer. A binding
fifth wheel could cause erratic steering and loss
of vehicle control, possibly resulting in serious
personal injury or death.
2.
The kingpin lock mechanism must be fully open,
and the fifth wheel plate must be completely lu-
bricated with chassis grease. For lubrication in-
structions, see Group 31 of the
Century Class
Trucks Maintenance Manual
.
3.
Position the tractor so that the fifth wheel lock
opening is in line (both vertically and horizontally)
with the trailer kingpin. The kingpin should be in
a position to enter the throat of the locking
mechanism, to prevent a false lockup. See
Fig. 10.5
. Adjust the trailer landing gear to give
enough alignment height so that the fifth wheel
picks up the trailer on the fifth wheel ramps.
4.
With the fifth wheel lock opening aligned with the
trailer kingpin, back the tractor slowly toward the
trailer, making sure that the kingpin correctly en-
ters the throat of the locking mechanism. When
the trailer is picked up by the fifth wheel, stop the
tractor, then continue slow backward motion until
positive lockup occurs.
5.
Apply the tractor parking brakes.
07/11/2000
f310841
2
2
1
1
4
3
3
5
A
B
A. Closed Position, Locked
B. Open Position, Unlocked
1.
Release Handle and Spring
2.
Adjustment Nut
3.
Lock Halves
4.
Lock Pivot
5.
Sliding Yoke
Fig. 10.4, Type "B" Kingpin Lock Mechanism (bottom view)
Fifth Wheels and Trailer Couplings
10.2