. Check the position of the tractor by using both
outside mirrors and by looking down both sides
of the trailer.
Step 4. Back slowly
l Back slowly until the fifth wheel just touches the
Step 5. Secure tractor
Apply the parking brake.
Place the manual transmission in neutral; if an
automatic transmission, place in park.
Place wheel chocks.
Step 6. Check height of trailer
. The trailer should be low enough to allow it to be
raised slightly by the tractor when the tractor is
backed under it. Raise or lower the trailer as
If the trailer is too low, the tractor
may strike and cause unnecessary
damage to both the rear of the tractor
and the nose of the trailer. If the trailer
is too high, it may not couple correctly.
. Ensure the kingpin and fifth wheel are aligned.
Step 7. Connect air lines to trailer
Inspect rubber grommets in the glad hands for
wear and tear.
Connect the tractor emergency air line to the
trailer emergency glad hands.
Connect the tractor service air line to the trailer
service glad hands.
Ensure air lines are safely supported so they
cannot be crushed or caught while the tractor is
backing under the trailer.
Step 8. Supply air to trailer
From the cab, push in the air supply knob to
supply air to the trailer brake system. Military
tractors are sometimes equipped with shutoff
valves that must be opened to supply air to the
trailer brake system.
Check the air pressure gauge and wait until the
air pressure is normal.
Apply and release trailer brakes, listen for the
sound of the trailer brakes being applied and
released. You should hear the brakes move when
applied and air escape when the brakes are
Check the air pressure gauge for signs of major
Step 9. Lock trailer brakes
. Pull out the air supply knob or apply the trailer
hand valve on the steering column to lock the
Step 10. Back under the trailer
Use the lowest reverse gear.
Back the tractor under the trailer until the kingpin
is locked into the fifth wheel.
Pull the tractor gently forward while the trailer
brakes are still engaged ensuring the trailer
kingpin is locked into the locking jaws of the fifth
Step 11. Inspect coupling
. Place the transmission in neutral, if manual; in
park, if an automatic transmission.
. Engage parking brakes.
. Disengage the trailer hand valve.
NOTE: Depending on your location, you may want
shut off the engine and take the key with you to
prevent someone from moving the truck while you are
. Inspect the area around the fifth wheel. Make
sure there is no gap between the upper and lower
fifth wheel. If there is a gap, something is wrong.
The kingpin may be on top of the closed locking
jaws; if so, the trailer can come loose easily.