3-6 TOWING THE SEMITRAILER
Driving the towing vehicle with the semitrailer
coupled behind requires constant attention to the
overall length of the combination. The “hinged-in-
the-middle” configuration of the tractor and semi-
trailer, load, and weight effect performance. Turn-
ing, passing, acceleration, braking, stopping, and
backup require special considerations. When exe-
cuting steep grades or turning tight curves, the
semitrailer must not be allowed to push the towing
vehicle, or jack knifing the semitrailer with the tow-
ing vehicle may result. Application of the semi-
trailer brakes to keep the semitrailer in tow will
help prevent this pushing. Braking should begin
before descending a hill or attempting a curve, to
assure control.
CAUTION
WHEN OPERATING SEMITRAILER, DO
NOT BACK OVER CURB. THIS WILL
CAUSE SEVERE DAMAGE TO UNDER-
CARRIAGE.
3-6.1
Make a moving test of the semitrailer
brakes at low, and medium speeds before
traveling at highway speed.
a.
The Anti-Lock Brake System (ABS) warning
lamp mounted at left rear side of the semi-
trailer should come on when power is sup-
plied to the ABS by turning the tractor
keyswitch on. The warning lamp should go off
once the semitrailer exceeds 4 mph. If the
warning lamp does not go off, a fault exists in
the semitrailer ABS. Once the vehicle speed
exceeds 4 mph, the light should remain off
unless a fault occurs or the keyswitch is
turned off, then on again.
CAUTION
IF A FAULT EXISTS IN THE SEMI-
TRAILER ABS, NORMAL BRAKING
WILL OCCUR, BUT WHEELS MAY
LOCK. SERVICE THE ABS AS SOON
AS POSSIBLE.
3-6.2
Monitor the air pressure gauge on the
dash of the towing vehicle. Pressure should
not fall below 90 psi at any time.
3-6.3
The semitrailer wheels track to the in-
side of the towing vehicle during turns. Thus,
turning corners requires a wide swing to pre-
vent “curb hopping”, and to allow the semi-
trailer wheels to clear any obstacle on the in-
side of the corner.
3-6.4
To stop, use a gradual and smooth ap-
plication of brakes. If grabbing occurs, apply
less pressure - grabbing brakes are not effi-
cient.
WARNING
ALWAYS CHECK BEHIND AND UNDER
THE TRUCK AND SEMITRAILER FOR
PERSONS OR OBJECTS BEFORE
MOVING. FAILURE TO CHECK CAN
LEAD TO SERIOUS PERSONAL IN-
JURY OR DEATH TO OTHERS, OR
DAMAGE TO PROPERTY.
3-6.5
Backing should be done with care. Tail
overhang, semitrailer length, and allowable
space must be taken into consideration when
backing the semitrailer.
3-7
Summary of Contents for 825A
Page 8: ......
Page 12: ......
Page 14: ...3 2 Figure 3 1 Model 825 Trailer Terminology Figure 3 2 Service Hookups...
Page 18: ...3 6 Figure 3 3 Hydraulic Controls...
Page 22: ...3 10 Figure 3 5 Swingout Outrigger Platform Extension...
Page 24: ...3 12 Figure 3 6 Gooseneck Attachment to Frame...
Page 34: ......
Page 36: ...4 2 Figure 4 1 Lubrication Points...
Page 40: ...4 6 Figure 4 2 Model 825A Wiring Diagram...
Page 43: ...4 9 Figure 4 4 Tandem Axle Air Ride Suspension System...
Page 44: ...4 10 Figure 4 5 Tandem Axle W Flip Air Ride Suspension System...
Page 47: ...4 13 Figure 4 8 Checking Axle Alignment Figure 4 9 Examples of Camber...
Page 52: ...4 18 Figure 4 12 Axle and Brake Assembly...
Page 59: ...4 25 Figure 4 18 Mounting Tires and Wheels Figure 4 19 Stud Tightening Sequence...
Page 69: ...NOTES 5 9...
Page 70: ......
