CDL Combination Vehicles TestCoupling and UncouplingEasy
A driver is uncoupling a trailer. After lowering the landing gear firmly to the ground and disconnecting the air and electrical lines, what is the next step to safely separate the tractor from the trailer?
- AChock the trailer wheels.
- BCrank the landing gear to lift the trailer slightly off the fifth wheel.
- CPull the fifth wheel release handle.
- DRelease the tractor's parking brake.
Show answer & explanationAnswer & explanation
Correct answer: C. Pull the fifth wheel release handle.
Once the landing gear is supporting the trailer and air/electrical connections are removed, the next immediate step is to release the fifth wheel to allow the tractor to pull away. Lifting the trailer with the landing gear before releasing the fifth wheel could damage the equipment.
Why the other options are wrong
- A. Chocking the trailer wheels should ideally be done before lowering the landing gear for stability.
- B. Lifting the trailer off the fifth wheel happens after the release handle is pulled, by slowly backing the tractor.
- D. This is done after the fifth wheel is released and the tractor is ready to pull away.
Fifth Wheel Release in Uncoupling
After securing the trailer on its landing gear and disconnecting utilities, the fifth wheel release handle must be pulled to disengage the kingpin, allowing the tractor to separate.
- Release handle opens fifth wheel jaws.
- Must be done before moving tractor.
- Ensures kingpin is free.
Memory trick: Lower, Disconnect, Release, Drive.