in the locked position. This prevents the sliding
member from moving rapidly to the far forward or
rearward position, which could damage the fifth
wheel member or kingpin.
2.
The fifth wheel jaw must be fully open. Make
sure that the operating rod is in the unlocked po-
sition. The fifth wheel must be completely lubri-
cated with chassis or multi-purpose grease. For
lubrication instructions, see Group 31 of the
Century Class Trucks Maintenance Manual
.
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.
3.
Make sure the fifth wheel top plate is tilted so the
ramps are as low as possible. If equipped with
an air suspension, make sure the air bags are
completely inflated.
4.
Position the tractor so that the center of the fifth
wheel is in line with the trailer kingpin. The king-
pin should be in a position to enter the throat of
the locking mechanism. See
Fig. 10.10
. Adjust
the trailer landing gear so that the lower front
trailer edge contacts the top surface of the tilted
fifth wheel plate, approximately 8 inches (20 cm)
before the fifth wheel center.
5.
With the fifth wheel lock opening aligned with the
trailer kingpin, back the tractor slowly toward the
trailer, making sure that the kingpin enters the
throat of the locking mechanism. Continue back-
ward motion until positive lockup occurs.
6.
Apply the tractor parking brakes.
7.
Make a visual check (even if equipped with the
Touchloc air-operated system) for positive king-
pin lockup. The trailer bed plate must be flush on
the fifth wheel plate surface. When positive
lockup has occurred, the fifth wheel operating
rod will have moved inward to the locked posi-
tion, and the safety latch will swing freely over
the operating rod. See
Fig. 10.12
.
NOTE: Only when the operating rod is fully re-
tracted in the locked position will the safety latch
be freely rotated down.
8.
Release the tractor parking brakes. Test for king-
pin lockup by pulling on the trailer against the
chocks.
NOTICE
Always make sure the connect-hanger/support
keeps the trailer air hoses and electrical cables
positioned so that they do not rub on anything.
Rubbing may wear through hoses or cables, re-
sulting in air leaks, or exposed or broken wires,
potentially affecting trailer brake or electrical sys-
tems.
9.
After lockup is completed, connect the tractor-to-
trailer air system lines and electrical cable to the
trailer. Take care to prevent dirt or foreign mate-
rial from entering the air system lines.
10. Charge the air brake system with air. Make sure
that the air connections do not leak.
WARNING
Adjust the jaw pin if there is more than 1/8-inch
(3-mm) clearance between the kingpin and the
lock. Incorrect adjustment could cause the trailer
to disconnect, possibly resulting in serious per-
sonal injury or death.
11. With the trailer wheels chocked and the brakes
set, check for clearance between the kingpin and
the fifth wheel jaws by moving the tractor forward
and backward against the locked kingpin. A
clearance of approximately 1/16 inch (1.6 mm)
between the jaw and kingpin is allowable. When
clearance between the jaw and kingpin exceeds
1
2
10/26/2010
f310448
1.
Safety Latch
2.
Operating Rod
Fig. 10.12, Simplex Kingpin Locking Mechanism, Safety
Latch (locked position)
Fifth Wheels and Trailer Couplings
10.8