Introduction
A tractor and a trailer are two separate units until they are brought together and joined, or coupled. It is the driver’
s responsibility to couple the tractor and trailer correctly for any trip. This chapter discusses how to couple and
uncouple a rig safely in a step-by-step sequence.
Coupling is a basic skill to be mastered by the professional driver operating any tractor-trailer rig. FMCSR require
all drivers to be qualified in this operation.
The best way to learn coupling is by using a 15-step approach that protects you and others from injury and your
vehicle and cargo from damage. Trying to couple or uncouple a rig without knowing this sequence can be
dangerous.
Typical hazards in coupling or uncoupling a rig include the following :
• When the tractor is not secured, brake lines can be damaged.
• When trailer brakes are not functioning, the trailer can be pushed into an obstruction.
• When the ground is not firm for uncoupling, the trailer can fall and become damaged.
• When trailer wheels are not chocked, the trailer may roll or be pushed into an obstruction and damaged.
• When climbing on the tractor during coupling, the driver could fall because of slippery surfaces
• If the driver works under an unsupported trailer (no jackstand or tractor under the trailers nose), he/she
could be injured if the landing gear collapses and trailer falls to the ground.
• The kingpin may be too shallow, or the tractor may be too long. Damage may result to the tractor, trailer, or
landing gear.
Step-by-step coupling procedures
Step 1: Inspect the Fifth Wheel
When inspecting the fifth wheel , you should check for damaged or missing parts as well as the mounting of the
fifth wheel on the tractor to be certain it is secure and not damaged. The fifth wheel must always have a coating of
grease applied to the retention groove to ensure smooth movement when the trailer is being turned.
Also check:
• The fifth wheel is in position for coupling and tilted down toward the rear of the tractor.
• The jaws are open.
• The safety release handle is in the automatic lock position.
• The slider locks are in place.
• The fifth wheel position will allow coupling without allowing the rear end of the tractor to strike the landing
gear.
Step 2: Inspect the Area and Choke the Trailer Wheels
Be sure the area is clear. Then chock the trailer wheels. Check the cargo to be sure it will not move when the
trailer is coupled to the tractor.
Step 3: Position the Tractor
The tractor should be placed squarely in front of the trailer. Do not back the tractor at an angle. The wrong
approach by the tractor can push the trailer backward or sideways. This can break the landing gear and cause
the trailer to fall.
To be sure the tractor and trailer line up properly, use the outside edge of your drive axle tires and the edge of
the trailer as guide points. The tractor, outside edge of the drive axle tires, and edge of the trailer should form a
straight line if the trailer is 96 inches (8feet) wide. With many of today’s trailers being 102 inches (8-1/2 feet) wide,
the tractor drive axle tries should be approximately 1-1/2 to 3 inches inside the outside edge of the trailer.
Note: Pulling up directly in front of the trailer for coupling is the preferred method, but in some situations you may
have to back in at an angle to the trailer. Do not hesitate to exit the cab as many times as necessary to site the
throat of the fifth wheel with the kingpin.
Step 4: Back Slowly until the Fifth Wheel Just Touches the Trailer
Back slowly toward the nose of the trailer and stop just before the fifth wheel reaches the trailer. You should be
close enough to hook up the air lines and to compare the fifth-wheel height with the trailer height.
Step 5: Secure the Tractor
Shift into neutral. Put on the tractor parking brake. Exit the cab.
Step 6: Check the Trailer Height
Inspect the height of the trailer nose compared to the fifth wheel. The nose should be slightly higher than the back
of the fifth wheel. To couple properly, the nose of the trailer should touch the middle of the fifth wheel.
To adjust the height of the trailer, crank the landing gear up or down. If the tractor has an adjustable air
suspension, you can adjust the fifth wheel to the correct height to couple with the trailer. If the trailer is too low,
the tractor may hit and damage it. If the trailer is too high, it may ride up and over the fifth wheel and into the rear
of the cab.
Step 7: Connect the Air Lines (If the Trailer is Not Equipped with Spring Brakes)
When the height of the trailer is correct, you are ready to connect the tractor’s air lines to the trailer. There are
two air lines running from the tractor to the trailer. They are called the Service and Emergency air lines. Normally,
one will be stamped “Service” and the other “Emergency.” Glad hands connect the air lines. Sometimes the air
lines are coded differently. They may be color coded ( red for emergency and blue or black for service) or shape
coded (round glad hands for the emergency air line and square glad hand for the service air line).
For the brakes to work properly, the air lines must be connected correctly. Match the plug to the connector. Do
not force it if it does not fit. Sometimes the tractor’s connectors and the trailer’s connectors do not match. Use a
converter if necessary. Firmly seat the plug in the receptacle. Put in the safety catch, or latch, to keep them from
accidentally separating.
Step 8: Supply Air to the Trailer
After the air lines have been connected and secured, get back into the cab. With the truck engine off, push in the
red trailer air supply valve to supply the trailer brakes with air. Listen for escaping air. If you hear a leak or if the
air pressure gauge registers excessive loss of sir, correct the problems. You will notice air leaking if you have
connected the air lines incorrectly.
Step 9: Release the Tractor Parking Brake and Put on the Trailer Brake
You are now ready to back the tractor under the trailer:
• Start the truck engine
• Put the truck into gear
• Release the tractor parking brake (yellow valve)
• If the trailer is not equipped with spring brakes, pull out the trailer air supply valve (red) to apply the trailer
brakes.
Step 10: Back Under the Trailer
Using the lowest reverse gear, back the tractor slowly under the trailer. Stop when you feel or hear the kingpin
lock into the fifth wheel.
Do not hit the kingpin too hard. This could bend the kingpin, buckle the upper plate, jump the pin (the kingpin
over the fifth wheel causes the trailer to hit the tractor), push the trailer away, or damage cargo in the trailer.
Step 11: Test the Connection
Test the hookup by pulling the tractor gently forward in low gear while the trailer hand brake is on. As soon as
resistance to forward motion is felt, disengage the clutch. Accelerate just enough to keep the engine from stalling.
Then test the connection again.
Step 12: Secure the Vehicle
When you are sure of a solid hookup, apply the parking brake. Turn off the engine, put key in pocket, and get out
of the cab.
Step 13: Inspect the Coupling
You will now need to go under the trailer and use a flashlight to get a good look at the coupling. Check that the
following are done:
• Fifth-wheel jaws have engaged the shank of the kingpin and not the head. If the jaws are closed around the
head, the trailer will bounce the kingpin out of the jaws.
• Jaws are closed and locked. The safety catch is over the locking lever.
• Upper fifth-wheel plate is in full contact with the lower trailer plate. There should be no gap between the
trailer apron and the fifth-wheel plate. If there is a space between the two, stop and fix the problem before doing
anything else. The space may be due to uneven ground surface. Move the rig to flat ground and check again.
Step 14: Connect the Electrical Cord, Then Check the Air Lines
Plug the electrical cord into the trailer. Then fasten the safety catch. Be sure neither the electrical cord nor the air
lines are damaged. These lines must not hit any moving parts of the rig.
Step 15: Raise the Landing Gear
You are now ready to raise the landing gear. Most crank handles have a low speed and a high speed. Use the low
speed to start raising the landing gear. Switch to high speed when the trailer weight is off the landing gear. Keep
on cranking until the landing gear is fully raised.
Step-by-step uncoupling procedures
Step 1: Position the Vehicle
To prepare the uncoupling, place the tractor directly in line with the trailer on level ground. This is to keep from
damaging the landing gear when pulling the tractor from under the trailer.
Make sure the surface where you plan to uncouple the trailer will support the rig and is level.
Step 2: Secure the Vehicle
Place the tractor protection valve in the emergency position. This cuts off the air supply between the tractor and
trailer. Make sure you have backed tightly against the pin. If not, it will bind and not replace properly. Put on the
tractor parking brake. Exit the cab.
Step 3: Lower the Landing Gear
Inspect landing gear for rust and damage. Then lower the landing gear until both supports touch the ground. If
one touches the ground but not the other, find a more level location to drop the trailer. Crank until you see the
trailer begin to rise off the fifth wheel.
A tractor and a trailer are two separate units until they are brought together and joined, or coupled. It is the driver’
s responsibility to couple the tractor and trailer correctly for any trip. This chapter discusses how to couple and
uncouple a rig safely in a step-by-step sequence.
Coupling is a basic skill to be mastered by the professional driver operating any tractor-trailer rig. FMCSR require
all drivers to be qualified in this operation.
The best way to learn coupling is by using a 15-step approach that protects you and others from injury and your
vehicle and cargo from damage. Trying to couple or uncouple a rig without knowing this sequence can be
dangerous.
Typical hazards in coupling or uncoupling a rig include the following :
• When the tractor is not secured, brake lines can be damaged.
• When trailer brakes are not functioning, the trailer can be pushed into an obstruction.
• When the ground is not firm for uncoupling, the trailer can fall and become damaged.
• When trailer wheels are not chocked, the trailer may roll or be pushed into an obstruction and damaged.
• When climbing on the tractor during coupling, the driver could fall because of slippery surfaces
• If the driver works under an unsupported trailer (no jackstand or tractor under the trailers nose), he/she
could be injured if the landing gear collapses and trailer falls to the ground.
• The kingpin may be too shallow, or the tractor may be too long. Damage may result to the tractor, trailer, or
landing gear.
Step-by-step coupling procedures
Step 1: Inspect the Fifth Wheel
When inspecting the fifth wheel , you should check for damaged or missing parts as well as the mounting of the
fifth wheel on the tractor to be certain it is secure and not damaged. The fifth wheel must always have a coating of
grease applied to the retention groove to ensure smooth movement when the trailer is being turned.
Also check:
• The fifth wheel is in position for coupling and tilted down toward the rear of the tractor.
• The jaws are open.
• The safety release handle is in the automatic lock position.
• The slider locks are in place.
• The fifth wheel position will allow coupling without allowing the rear end of the tractor to strike the landing
gear.
Step 2: Inspect the Area and Choke the Trailer Wheels
Be sure the area is clear. Then chock the trailer wheels. Check the cargo to be sure it will not move when the
trailer is coupled to the tractor.
Step 3: Position the Tractor
The tractor should be placed squarely in front of the trailer. Do not back the tractor at an angle. The wrong
approach by the tractor can push the trailer backward or sideways. This can break the landing gear and cause
the trailer to fall.
To be sure the tractor and trailer line up properly, use the outside edge of your drive axle tires and the edge of
the trailer as guide points. The tractor, outside edge of the drive axle tires, and edge of the trailer should form a
straight line if the trailer is 96 inches (8feet) wide. With many of today’s trailers being 102 inches (8-1/2 feet) wide,
the tractor drive axle tries should be approximately 1-1/2 to 3 inches inside the outside edge of the trailer.
Note: Pulling up directly in front of the trailer for coupling is the preferred method, but in some situations you may
have to back in at an angle to the trailer. Do not hesitate to exit the cab as many times as necessary to site the
throat of the fifth wheel with the kingpin.
Step 4: Back Slowly until the Fifth Wheel Just Touches the Trailer
Back slowly toward the nose of the trailer and stop just before the fifth wheel reaches the trailer. You should be
close enough to hook up the air lines and to compare the fifth-wheel height with the trailer height.
Step 5: Secure the Tractor
Shift into neutral. Put on the tractor parking brake. Exit the cab.
Step 6: Check the Trailer Height
Inspect the height of the trailer nose compared to the fifth wheel. The nose should be slightly higher than the back
of the fifth wheel. To couple properly, the nose of the trailer should touch the middle of the fifth wheel.
To adjust the height of the trailer, crank the landing gear up or down. If the tractor has an adjustable air
suspension, you can adjust the fifth wheel to the correct height to couple with the trailer. If the trailer is too low,
the tractor may hit and damage it. If the trailer is too high, it may ride up and over the fifth wheel and into the rear
of the cab.
Step 7: Connect the Air Lines (If the Trailer is Not Equipped with Spring Brakes)
When the height of the trailer is correct, you are ready to connect the tractor’s air lines to the trailer. There are
two air lines running from the tractor to the trailer. They are called the Service and Emergency air lines. Normally,
one will be stamped “Service” and the other “Emergency.” Glad hands connect the air lines. Sometimes the air
lines are coded differently. They may be color coded ( red for emergency and blue or black for service) or shape
coded (round glad hands for the emergency air line and square glad hand for the service air line).
For the brakes to work properly, the air lines must be connected correctly. Match the plug to the connector. Do
not force it if it does not fit. Sometimes the tractor’s connectors and the trailer’s connectors do not match. Use a
converter if necessary. Firmly seat the plug in the receptacle. Put in the safety catch, or latch, to keep them from
accidentally separating.
Step 8: Supply Air to the Trailer
After the air lines have been connected and secured, get back into the cab. With the truck engine off, push in the
red trailer air supply valve to supply the trailer brakes with air. Listen for escaping air. If you hear a leak or if the
air pressure gauge registers excessive loss of sir, correct the problems. You will notice air leaking if you have
connected the air lines incorrectly.
Step 9: Release the Tractor Parking Brake and Put on the Trailer Brake
You are now ready to back the tractor under the trailer:
• Start the truck engine
• Put the truck into gear
• Release the tractor parking brake (yellow valve)
• If the trailer is not equipped with spring brakes, pull out the trailer air supply valve (red) to apply the trailer
brakes.
Step 10: Back Under the Trailer
Using the lowest reverse gear, back the tractor slowly under the trailer. Stop when you feel or hear the kingpin
lock into the fifth wheel.
Do not hit the kingpin too hard. This could bend the kingpin, buckle the upper plate, jump the pin (the kingpin
over the fifth wheel causes the trailer to hit the tractor), push the trailer away, or damage cargo in the trailer.
Step 11: Test the Connection
Test the hookup by pulling the tractor gently forward in low gear while the trailer hand brake is on. As soon as
resistance to forward motion is felt, disengage the clutch. Accelerate just enough to keep the engine from stalling.
Then test the connection again.
Step 12: Secure the Vehicle
When you are sure of a solid hookup, apply the parking brake. Turn off the engine, put key in pocket, and get out
of the cab.
Step 13: Inspect the Coupling
You will now need to go under the trailer and use a flashlight to get a good look at the coupling. Check that the
following are done:
• Fifth-wheel jaws have engaged the shank of the kingpin and not the head. If the jaws are closed around the
head, the trailer will bounce the kingpin out of the jaws.
• Jaws are closed and locked. The safety catch is over the locking lever.
• Upper fifth-wheel plate is in full contact with the lower trailer plate. There should be no gap between the
trailer apron and the fifth-wheel plate. If there is a space between the two, stop and fix the problem before doing
anything else. The space may be due to uneven ground surface. Move the rig to flat ground and check again.
Step 14: Connect the Electrical Cord, Then Check the Air Lines
Plug the electrical cord into the trailer. Then fasten the safety catch. Be sure neither the electrical cord nor the air
lines are damaged. These lines must not hit any moving parts of the rig.
Step 15: Raise the Landing Gear
You are now ready to raise the landing gear. Most crank handles have a low speed and a high speed. Use the low
speed to start raising the landing gear. Switch to high speed when the trailer weight is off the landing gear. Keep
on cranking until the landing gear is fully raised.
Step-by-step uncoupling procedures
Step 1: Position the Vehicle
To prepare the uncoupling, place the tractor directly in line with the trailer on level ground. This is to keep from
damaging the landing gear when pulling the tractor from under the trailer.
Make sure the surface where you plan to uncouple the trailer will support the rig and is level.
Step 2: Secure the Vehicle
Place the tractor protection valve in the emergency position. This cuts off the air supply between the tractor and
trailer. Make sure you have backed tightly against the pin. If not, it will bind and not replace properly. Put on the
tractor parking brake. Exit the cab.
Step 3: Lower the Landing Gear
Inspect landing gear for rust and damage. Then lower the landing gear until both supports touch the ground. If
one touches the ground but not the other, find a more level location to drop the trailer. Crank until you see the
trailer begin to rise off the fifth wheel.
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