TM-9-2320-272-10
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; OPERATOR'S MANUAL
SEPTEMBER 2004
CHANGE 2
TM-9-2320-272-10 - Page 253 of 481
TM 9-2320-272-10
2-152
2-26. OPERATION OF TRACTOR AND FIFTH WHEEL
a.
General.
A fifth wheel, or semitrailer coupler, is mounted on the rear of
M931/A1/A2 and M932/A1/A2 tractor trucks. When connected to a semitrailer, the
fifth wheel pivots up, down, and sideways to allow for changes in road conditions. The
fifth wheel is rated at 37,500 lb (17,025 kg) cross-country.
b.
Wedge Adjustment.
(1)
Position fifth wheel wedges (13) fully below walking beam (10) for
highway operations.
(2)
Position wedges (13) back and away from walking beam (10) for cross-
country operations.
(3)
To position wedges:
(a)
Remove screws (14) from center wedges (13).
(b)
Remove wedge (13) and reverse position.
(c)
Install screws (14) on center wedges (13) and tighten.
c.
Coupling Semitrailer.
.
WARNING
.
When backing up, maintain centerline of tractor with centerline
of semitrailer and use ground guide.
(1)
Back up tractor so fifth wheel coupler jaws (11) are directly in line
with semitrailer kingpin (3).
(2)
Stop tractor in front of semitrailer, place transmission shift lever (8)
in N (neutral), and apply parking brake (9).
(3)
Turn landing gear crank (4) to adjust semitrailer height to tractor.
Semitrailer approach plates (2) should be slightly lower than tractor fifth wheel (1).
(4)
Block semitrailer wheels with chocks (5).
(5)
Pull plunger handle (12) forward, then out, to open fifth wheel
coupling jaws (11).
(6)
Release parking brake (9) and slowly back tractor under semitrailer.
Place transmission selector (8) in N (neutral) and apply parking brake (9).
.
WARNING
.
Make sure to connect service hose to service coupling and
emergency hose to emergency coupling. Hoses not properly
connected will cause brake failure.
(7)
Connect tractor air coupling (15) to semitrailer air couplings (16).
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