Page 98 - Driving Commercial Vehicles Manual+

chapter 5 — skills for driving trucks and trailers

Uncoupling units

Use these steps to uncouple a tractor and trailer joined with a fifth wheel:
1. Position the tractor and trailer
Move forward/backward so that the tractor is directly in line with the trailer (not at
an angle).

❏ Tractor and trailer • if you’re lined up, you should be able to
position see both sides of the trailer in the exterior
mirrors • ensure the road or ground surface
is level and will support the trailer

Yes

No

Make sure that the tractor
and trailer are lined up
before uncoupling.

2. Ease pressure on the fifth wheel locking jaws
Set the trailer brakes and release tractor brakes.

Back up gently and apply tractor parking brakes while the tractor is pushing
driving tip against the trailer.

The tractor may only move
a few centimetres, but this ❏ Fifth wheel locking • back up the tractor to relieve pressure of
will ease pressure on the fifth jaws the fifth wheel locking jaws on the trailer
wheel locking jaws. kingpin

3. Prepare to uncouple
Exit cab.
fast fact
Block trailer wheels.
Both landing gear supports Place blocks or pads under the trailer landing gear if needed.
must touch the ground to
support a trailer. Lower the trailer landing gear until both supports touch the ground and
pressure is released off the fifth wheel.
Disconnect air lines and electrical cable and secure lines to tractor.

Pull the fifth wheel release handle to unlock the fifth wheel jaws.

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