Coupling & UncouplingQuestion 7 of 60
When should the locking jaws be closed around the kingpin?
a.Around the top head of the kingpin
b.Loosely, so the trailer can pivot freely
c.Around the shank of the kingpin, with no gap between the upper and lower fifth wheel plates
d.Only after the landing gear is fully lowered
Explanation
The locking jaws must close around the shank of the kingpin, and there should be no space between the upper and lower fifth wheel plates. If the jaws close on the head of the kingpin, the coupling can come apart. A gap between the plates indicates a bad coupling that must be corrected before driving.
Practice all 60 questions free — no signup required.
Related questions on this topic
- When connecting the glad hands, what must you check to avoid a dangerous coupling mistake?
- After the kingpin has locked into the fifth wheel, how should you test that the coupling is secure?
- After the tug test, why should you go under the trailer and look into the back of the fifth wheel?
- After the trailer is securely coupled and supported by the tractor, what should you do with the landing gear?
- Before supplying air to the trailer, why should you check the trailer brakes are set?
- When you push the trailer air supply valve in (supply air to trailer), what should happen?
Last reviewed: · editorial process
PrepPass Editorial Team · Verified against CDL Combination Vehicles Knowledge Test · How we review