conbinatio n

You should not back a tractor under a trailer until the whole air system is:

• At normal pressure

• Bled down to half the maximum pressure

• Between 60 and 80 psi

• Empty

Before you back under a trailer, make sure the:

• Trailer brakes are locked

• Trailer protection valve is normal

• Air brakes are off

• Air supply knob is in

You are coupling a semi trailer to your tractor but have not yet backed under. The trailer is at the right height when:

• The kingpin is about 1 ½ inches above the fifth wheel

• The end of the kingpin is even with the top of the fifth wheel

• It will be raised slightly when the tractor is backed under it

• The trailer landing gear is fully extended

You are coupling a tractor to a semi trailer and have backed up but are not under it. What should you hook up before backing under?

• Electrical service cable

• The emergency and service air lines

• The ground cable

• The left rear outer dual wheel with the kingpin

When you get ready to back under the semi trailer you should line up:

• About 12 degrees off the line of the trailer

• The kingpin to engage the drivers side locking jaw first

• Directly in front of the trailer

• The left rear outer dual wheel with the kingpin

If the service air line comes apart while you are driving a combination vehicle but the emergency line stays together, what will happen right away?

• The emergency tractor brakes will come on

• The trailer’s air tank will exhaust through the open line

• Nothing is likely to happen until you try to apply the brakes

• The emergency trailer brakes will come on

Which part of the kingpin should the locking jaws close around?

• The shank

• The head

• The base

• It does not matter

The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means that:

• You can set the fifth wheel for weight balance

• The parking lock is off and you can drive away

• The coupling is not right and should be fixed before driving the coupled unit

• The trailer will not swivel on the fifth wheel

How should you test the tractor-semi trailer connection for security?

• Put the tractor in gear and pull with a sharp jerk

• Pull gently forward in low gear against the locked trailer brakes. Then look at it carefully

• Rock the trailer back and forth with the trailer brakes locked

• Look at it carefully

The air leaking rate for a combination vehicle (engine off, brakes on) should be less than _____ psi per minute.

• 1

• 2

• 3

• 4