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Coupling and Uncoupling
Knowing how to couple and uncouple correctly is basic to safe operation of combination vehicles. General
coupling and uncoupling steps are listed below. There are differences between different rigs. So learn the
details of coupling and uncoupling the truck(s) you operate.
CAUTION!
INCORRECT COUPLING AND UNCOUPLING CAN RESULT IN SERIOUS INJURY OR DEATH.
Coupling Tractor-Semi trailers
Step 1 Inspect Fifth Wheel
• Check for damaged/missing parts.
• Check to see that mounting to tractor is secure, no cracks in frame, etc.
• Be sure that the fifth wheel plate is greased as required. Failure to keep the fifth wheel plate
lubricated could cause steering problems because of friction between the tractor and the trailer.
• Check if fifth wheel is in proper positioning for coupling.
o Wheel tilted down towards rear of tractor.
o Jaws open.
o Safety unlocking handle in the automatic lock position.
• If you have a sliding fifth wheel, make sure it is locked.
• Make sure the trailer kingpin is not bent or broken.
Step 2 Inspect Area and Chock Wheels
• Make sure area around vehicle is clear.
• Be sure trailer spring brakes are on.
• Check that cargo (if any) is secured against movement due to tractor being coupled to trailer.
Step 3 Position Tractor
• Put the tractor directly in front of the trailer. (Never back under the trailer directly at an angle,
because you might push the trailer sideways and break the landing gear.)
• Check position, using outside mirrors, by looking down both sides of the trailer.
Step 4 Back Slowly
• Back until fifth wheel touches the trailer.
• Don't hit the trailer.
Step 5 Secure Tractor
• Put on parking brake.
• Put transmission in neutral.
Step 6 Check Trailer Height
• The trailer should be low enough that it is raised slightly by the tractor when the tractor is backed
under it. Raise or lower the trailer as needed. (If trailer is too low, tractor may strike and damage
nose of trailer; if trailer is too high, it may not couple correctly.) Check that the kingpin and fifth
wheel are aligned.
Step 7 Connect Air Lines to Trailer
• Check glad hand seals and connect tractor supply (emergency) airline to trailer supply (emergency)
glad hand.
• Check glad hand seals and tractor control (service) airline to trailer control (service) glad hand.
• Make sure airlines are safely supported where they won't be crushed or caught while tractor is
backing under trailer.
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