Tag Axle; Unloading Tag Axle (Optional) - PREVOST H3-41 Maintenance Manual

If the axle has been removed for repairs or
servicing and if all the parts are reinstalled
exactly in the same place, the axle alignment is
not necessary. However, if the suspension
supports have been replaced or altered, proceed
with the following instructions to verify or adjust
the drive axle alignment.
NOTE
When drive axle alignment is modified, tag
axle alignment must be re-verified.
3.5.1 Procedure
1. Park vehicle on a level surface, then chock
front vehicle wheels.
2. Using two jacking points (which are at least
30 inches [76 cm] apart) on drive axle, raise
the vehicle sufficiently so that wheels can
turn freely at about ½ inch from ground.
Secure in this position with safety stands,
and release parking brake.
3. Install wheel mount sensors on front end
and drive axle wheels (Figure 7).
NOTE
Select axle specifications in the appropriate
chart.
4. With the system installed as in Figure 7,
adjust drive axle according to specifications'
chart below.
DRIVE AXLE ZF A-132
Minimum
Thrust angle
Total toe
4.

TAG AXLE

The tag axle is located behind the drive axle. It
carries a single wheel and tire on each side.
One optional system allows unloading of the tag
axle air springs without raising the axle, while the
other system enables unloading and raising of
the tag axle (refer to the "OPERATOR'S
MANUAL" for location of controls). Both of these
systems have been designed for the following
purposes:
1. Shortening of wheelbase, thus allowing
tighter turning in tight maneuvering areas
such as parking lots or when making a
sharp turn.
2. Transferring extra weight and additional
traction to the drive wheels on slippery
surfaces.
CAUTION
Do not use tag axle in raised position for an
extended period. Raising tag axle increases
load on the drive axle, suspension and tires.
Do not drive vehicle with tag axle raised when
speed is exceeding 9mph (15 km/h).
In order to prevent damage to the suspension,
always raise the tag axle before lifting the
coach.
The tag axle service brakes operate only when
the axle is in normal driving (loaded) position.
4.1

UNLOADING TAG AXLE (OPTIONAL)

To reduce the turning radius, the air springs
pressure will be automatically reduced by 75%
when the coach is moving at speed lower than 5
mph (8 km/h) and with more than 1½ turn from
the steering.
PA1621 Maintenance Manual All Series | January 2017
SECTION 11: REAR AXLES
Nominal Maximum
value value
±0.11°
0.15°
0°
toe-in
value
0.15°
toe-out
17