OPERATION OF TRACTOR AND FIFTH WHEEL
General. A fifth wheel, or semitrailer coupler, is mounted on the rear of M931/Al/A2 and M932/Al/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.
Position fifth wheel wedges (13) fully below walking beam (10) for highway operations.
Position wedges (13) back and away from walking beam (10) for cross- country operations.
To position wedges:
Remove screws (14) from center wedges (13).
Remove wedge (13) and reverse position.
Install screws (14) on center wedges (13) and tighten.
c. Coupling Semitrailer.
When backing up, maintain centerline of tractor with centerline of semitrailer and use ground guide.
Back up tractor so fifth wheel coupler jaws (11) are directly in line with semitrailer kingpin (3).
Stop tractor in front of semitrailer, place transmission shift lever (8) in N (neutral), and apply parking brake
Turn landing gear crank (4) to adjust semitrailer height to tractor. Semitrailer approach plates (2) should be
slightly lower than tractor fifth wheel (1).
Block semitrailer wheels with chocks (5).
Pull plunger handle (12) forward, then out, to open fifth wheel coupling jaws (11).
Release parking brake (9) and slowly back tractor under semitrailer. Place transmission selector (8) in N
(neutral) and apply parking brake (9).
Make sure to connect service hose to service coupling and emergency hose to emergency coupling.
Hoses not properly connected will cause brake failure.
Connect tractor air coupling (15) to semitrailer air couplings (16).