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27
Alignment & Adjustments
ULTIMAAX
®
for Fire and Rescue Vehicles
SECTION 7
Alignment & Adjustments
AXLE ALIGNMENT
■
The primary control for axle alignment
is the location of the frame hanger assemblies on
the frame rail as installed by the vehicle manufacturer, and the location of the axle brackets
on the axles as installed by the axle or vehicle manufacturer .
■
Axle centering and pinion angles
are controlled by the torque rods .
■
Ride height
is controlled by the design of the suspension frame hanger . No adjustment is
possible .
DRIVE AXLE PINION ANGLE
Drive axle pinion angles are established by the vehicle manufacturer . If pinion angle adjustment
is required, check for proper angles with the vehicle manufacturer . Pinion angle is set by the lon-
gitudinal torque rod length .
TO CHECK THE PINION ANGLE
FIGURE 7-1
1 . Use a work bay with a level
floor .
2 . Relax the suspension by
slowly moving the vehicle
back and forth several times
in a straight line without using
the brakes . This will slacken or
loosen the suspension as the
vehicle is positioned . End with
all wheels positioned straight
ahead . Roll to a stop without
the brakes being applied . DO NOT set the parking brake .
3 . Chock the front wheels of the vehicle .
4 . Place a digital protractor on the axle housing as shown in Figure 7-1 .
5 . Check to see if the pinion angle is correct per the vehicle manufacturer’s specified range .
6 . If necessary, add/remove shims at the longitudinal torque rod connections as required to
achieve the proper pinion angle .
7 . When the pinion angle is correct tighten all fasteners to the proper torque specifications per
the vehicle manufacturer and recheck the pinion angles .
8 . Remove wheel chocks .
DRIVE AXLE ALIGNMENT
NOTE
Drive axle alignment with suspensions equipped with
adapter style equalizing beam
end con-
nections
ARE NOT
adjustable .
Computerized alignment equipment is the preferred method of measuring alignment . To calculate
the shim thickness required, the target offset must be converted to thrust angle, see alignment
equipment manufacturer for procedures . If, however, computerized axle alignment equipment is
not available refer to the following Inspection in this section .