Mack CHM 2010, Operator'S Handbook Manual

Page: 141 / 232

OPERATION 133
COUPLING A TRAILER
1. Position the tractor directly in front of the trailer.
2. Back the trailer slowly until the fifth wheel just contacts the trailer plate.
3. Place the transmission in neutral and apply the parking brakes.
4. Connect the trailer glad hands and electrical connector.
CAUTION
Make sure the trailer air lines and the trailer electrical cord are properly supported so they
will not be pinched or caught while the tractor is being backed under the trailer.
5. Check that the fifth wheel height matches the height of the underside of the trailer. If the
trailer is too high, use the landing gear to lower the trailer until fifth wheel and trailer height
match. If the vehicle is equipped with an air suspension and the trailer is too low, use the
air suspension control switch to exhaust air from the suspension air bags until fifth wheel
and trailer height match.
CAUTION
Failure to match fifth wheel height with
trailer height will result in the trailer being
improperly connected.
6. Back under the trailer slowly until the trailer king pin engages. Back slowly to avoid
hitting the king pin too hard, and stop as soon as the king pin is locked into the fifth wheel.
7. If equipped with an air suspension, use the air suspension control switch to reinflate
the suspension air bags.
8. Raise the trailer landing gear slightly off the ground.
9. With the trailer parking brakes applied, pull the tractor ahead slightly to ensure that the
trailer is locked onto the tractor.
10. Push the trailer air supply valve (red octagonal knob) in to supply the trailer system with
air pressure. With the air system at normal operating pressure, check the trailer air brake
system for excessive leakage and proper operation.
11. Inspect the coupling to ensure the trailer is properly connected. Make sure there is no
space between the fifth wheel and the trailer plate and that the fifth wheel jaws have closed
around the shank of the king pin. Check that the locking lever is in the "lock" position and
make sure the safety latch is in position over the locking lever.
12. After ensuring that the trailer is properly connected, raise the landing gear to its
maximum height.
13. If wheel chocks were placed at the trailer wheels, remove the chocks and store.