Coupling & Uncoupling Trailers

A trailer that isn’t locked to the fifth wheel can drop onto the frame, or come off completely on the road. Drivers have also been crushed when a trailer rolled or dropped while they were between the tractor and trailer. Do it the same careful way every time.

• Truck drivers
• Class A CDL

Coupling

1. Inspect the area and the fifth wheel: clear the path, check that the fifth wheel is greased, tilted down toward the trailer, and the jaws are open with the release handle in the open position.
2. Check the trailer: wheels chocked or trailer brakes set, kingpin and apron undamaged, cargo secured.
3. Line up: back slowly so the fifth wheel is lined up with the kingpin.
4. Check trailer height: the trailer should be slightly lower than the center of the fifth wheel so it gets lifted slightly when you back under. Adjust the landing gear if needed.
5. Connect air lines (and electrical cord, per your procedure) and charge the trailer air supply. Check that the trailer brakes hold.
6. Back under slowly until the fifth wheel locks around the kingpin. Don’t slam into it.
7. Tug test: with trailer brakes applied, pull gently forward in low gear to make sure the trailer is locked. Do it more than once.
8. Get out and look: use a flashlight. The jaws must be closed around the kingpin shank, the locking lever in the locked position, and there must be no space between the upper and lower fifth wheel.
9. Raise the landing gear fully and secure the crank handle.
10. Remove chocks and do your walk-around.

Uncoupling

1. Park on firm, level ground that will support the landing gear. Line up straight.
2. Set the parking brakes and chock the trailer wheels if it doesn’t have spring brakes.
3. Lower the landing gear until it firmly contacts the ground, and take a little weight off the fifth wheel.
4. Disconnect the air lines and electrical cord and store them so they won’t be damaged.
5. Pull the fifth wheel release handle.
6. Pull the tractor forward partly, so the fifth wheel is just clear of the kingpin but the tractor frame is still under the trailer, and check that the landing gear is holding the trailer.
7. Pull clear.

Stay safe around the coupling

• Don’t crawl under a trailer that isn’t supported and chocked.
• Don’t stand between the tractor and trailer while anyone is in the cab.
• Don’t pull the release handle with your body in line with the tractor wheels.
• Don’t use the trailer hand valve as a parking brake.
• Don’t stand on a slick catwalk without good footing; use the grab handles. See Three Points of Contact.

Last updated: October 2, 2026