Truck Tips: How to couple and uncouple a trailer (video)
After you arrive at the yard and identify the trailer you are to pick up, scan the area in front of the trailer for obstacles before backing under it. And double check the unit number before you hook up.
If the area is clear and you have the correct trailer, get set up to back the tractor under the trailer, but stop before the fifth wheel contacts the trailer.
Exit the cab, maintaining three-point contact as you climb down, then visually inspect the king pin and the upper coupler plate for damage or deformities.
Visually confirm the locking mechanism of the 5th wheel is open, and the 5th wheel and trailer are compatible in height. Place wheel chocks under the trailer wheels to prevent it from rolling back when you hook up.
When the inspection is complete, re-enter the cab and prepare to reverse under the trailer. Before reversing, roll down the driver’s window and turn off the radio so you can hear the locking take place, or hear someone shouting a warning. Activate your four-way flashers and sound the horn before reversing. Put the transmission in reverse and release the tractor parking brakes.
Begin backing toward the trailer, but before connecting, confirm alignment of the tractor and trailer. Looking in the mirror, the tractor wheels should be about three inches inside of the side of the trailer for a 102-inch wide trailer. With a 96-inch wide trailer, the tractor tires and the side of trailer should be aligned.
You will feel a slight bump and some resistance as the 5th wheel contacts the trailer. Continue easing back until you feel the units connect. Listen for a clank sound as the locking mechanism engages — and, of course, the tractor will not be able to back any further.
Place the transmission in drive and gently tug forward to confirm the units are securely coupled.
The next step is a visual inspection to ensure the 5th wheel is properly locked and the units are coupled correctly. Place the transmission in neutral, set the tractor parking brake and exit the cab. Ensure the 5th wheel lock handle is in the locked position, and that there is no gap between the 5th wheel top plate and the trailer pick-up plate. Then look into the opening of the 5th wheel to verify the jaws of the fifth wheel or the locking bar are engaged in the throat of the 5th wheel.
Finally, raise the landing gear and stow the handle in the clip.
Connect the air and electric lines to the trailer and finish up with the prescribed vehicle inspection of the trailer, including, body, crossmembers, suspension, lights, tires, etc.
Retrieve your wheel chocks and you’re done.
How to uncouple a trailer
When uncoupling, look for a suitable spot to drop the trailer. The ground should be firm and level, preferably on concrete or asphalt if the trailer is loaded. Back the trailer into position then set the brakes and place the transmission in neutral. Exit the cab and confirm the landing gear legs are over the spot you intend to drop it, then place your wheel chocks around the trailer wheels.
Wind down the landing gear until it’s just above the ground or just touching the ground. Do not attempt to lift the trailer off the 5th wheel. When you deflate the air suspension, the trailer will settle firmly to the ground, but you don’t want to leave the tractor frame dangling by the 5th wheel, which is still connected to the trailer.
Pull the 5th wheel locking mechanism then disconnect the air and electrical lines and stow them in the rack at the back of the tractor and re-enter the cab.
When you’re ready to de-couple, release the tractor parking brakes, then, if equipped, flip the switch to deflate the tractor air suspension. Pause for a couple of seconds to allow some of the suspension pressure to bleed off, then gently pull the tractor forward.
Pull forward just far enough so that the 5th wheel is out from under the trailer, but the tractor frame is still under the trailer. If the ground gives way or the landing gear fails, the trailer will still be supported by the rear end of the tractor.
Set the tractor parking brakes and place the transmission in neutral then exit the cab. Perform a visual inspection of the ground under the landing hear legs to ensure the trailer is firmly supported.
Once you are sure the trailer is secure, re-inflate the tractor suspension, release the brake and drive on to the next trailer.
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I do not believe in chaulking the trailer. I want to know if the trailer moves at all while backing under it as that tells me the brakes are not working properly. If you do chaulk the trailer when dropping it do Not forget to retrieve your chaulks when you are clear of the trailer.