Jost Fifth Wheel Coupling
- Chock the front and rear of the trailer tires to prevent the trailer from moving.
- Tilt the fifth wheel ramps down.
- Unlock the fifth wheel jaws.Lift the release handle up into the wide slot and then pull the release handle out while moving it forward as shown in Fig. Lock the handle into the open position on the notch provided.
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Lift the release handle up into the wide slot.
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Pull the handle out.
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While pulling the handle out, move it forward.
Fig. 1, Unlocking the Jost Fifth Wheel
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- Back the vehicle close to the trailer, centering the kingpin
on the fifth wheel throat as shown in Fig.
Fig. 2, Positioning the Tractor
- Adjust the trailer height (if required).
For a standard fifth wheel plate , the trailer should contact the fifth wheel the top of the approach ramps or approximately 4 to 6 inches (10 to 20 cm) behind the pivot point as shown in Fig..For a low-lube fifth wheel plate , the trailer should contact the fifth wheel at the pivot point and the fifth wheel must slide freely under the trailer as shown in Fig.
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Fifth wheel must lift trailer
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Adjust trailer height
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Ramps tilted down
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4 to 8 inches
Fig. 3, Trailer Connection Point, Standard Fifth Wheel
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Adjust trailer height
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Ramps tilted down
Fig. 4, Trailer Connection Point, Low-Lube Fifth Wheel
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- Back the tractor slowly toward the trailer.On a standard fifth wheel , the fifth wheel must lift the trailer.On a no- or low-lube fifth wheel , do not lift the trailer. Lifting the trailer with a no- or low-lube fifth wheel may damage the fifth wheel plate.After lifting or sliding under the trailer, stop. This is to prevent hitting the kingpin too hard. Then resume backing up slowly until the fifth wheel locks.
- Apply the tractor parking brake, then perform a physical
check for positive kingpin lockup.
Depending on the fifth wheel model, the handle should be fully retracted with the handle inside the narrow slot as shown in Fig. or the release handle should abut the casting as shown in Fig.There should be no gap between the trailer and the fifth wheel.
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Verify the handle is inside the narrow slot.
Fig. 5, Locked Jost Fifth Wheel
Fig. 6, Jost Release Handle Locked
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- Release the tractor parking brakes and test for kingpin lockup by slowly moving the tractor forward, pulling the trailer against the chocks.
- After lockup is verified, connect the tractor-to-trailer air system lines and the electrical cable to the trailer. Take care to prevent dirt or foreign material from entering the air system lines
- Charge the air brake system with air, checking that the air connections do not leak.
- Fully retract the landing gear legs and secure the crank handle.
- Remove the chocks.
Notice: Attempting to couple at the wrong height may cause improper coupling, which could result in damage to the fifth wheel or kingpin.
Warning: A visual inspection is required by law.
Some improper couplings can pass a pull test. Sound is not reliable.
Get out of the cab and look.
Incorrect coupling could cause the trailer to disconnect, possibly resulting in serious personal injury or death.
Notice: Always make sure the connection hanger keeps the trailer air hoses and electrical cables positioned so that they do not rub on anything. Rubbing may wear through hoses or cables, resulting in air leaks, or exposed or broken wires, potentially affecting trailer brake or electrical systems.