4. R e c h e c k e q u a l i z i n g beam end connections for signs of looseness.
Inspect alignment shims in equalizing beam end for looseness. Lightly tap on the alignment shims to see if they can be moved. If movement is detected, tighten fasteners to the
proper torque value, see Figure 6-2.
■■ Inspect equalizing beam end connection for signs of excessive wear or looseness.
5. If bar pin looseness is still detected in any of the equalizing beam end hub, DO NOT operate
the vehicle. One or more components will require replacement, see Component Replacement
Section of this publication.
■■

■■

Adapter Style, see Figure 6-5
FIGURE 6-5

VISUAL INSPECTION
1. Chock the wheels.
2. Visually inspect suspension
components for signs of movement or excessive wear.
■■

■■

Preventive Maintenance

Inspect the equalizing
beam end connection for
signs of excessive wear or
looseness.
Look for worn, frayed or
distorted rubber in the beam, see Figure 6-6.
16

17730-299

ULTIMAAX® for Fire and Rescue Vehicles
■■
■■

Look for the equalizing beam to be lower in the axle bracket, see Figure 6-6.
If the adapter style end bushing is visually offset, a floor jack test should be performed,
refer to Jack Test in this section.

FIGURE 6-6

WORN BUSHING

GOOD BUSHING
Axle Bracket

Axle Bracket

C
L

C
L

A GOOD bushing will result in the equalizing
beam end hub appearing to be centered
with the centerline of the end bushing
in the axle bracket

A WORN bushing will result in the equalizing
beam end hub appearing to be 5/8" (15 mm)
offset/below the centerline of the end bushing
in the axle bracket

FIGURE 6-7

3. The beam end adapter style connections have
the flange of the adapter cut off for assembly
clearance with the axle housing bowl.
■■

The flat must be positioned vertically as
shown in Figure 6-7. If the flat of the adapter
position is incorrect, removal of the fasteners will be necessary to correct position,
refer to the Adapter Style End bushings in
the Component Replacement Section.

Axle Bracket
Adapter
Equalizing
Beam

Chisel Reliefs

JACK TEST

Adapter
Flat Side
Vertical

FIGURE 6-8

1. Place a jack under each beam end as shown.
Raise the jack to check for movement in
the connection or rubber components, see
Figure 6-8.
NOTE

The gap at each side of the visible rubber on the
lower part of the bar pin end bushing is normal,
see Figure 6-8, and is not an indication to replace
the bushing. Because all rubber end bushings are
in compression, with the load bearing on the top
side, the lower side of the rubber is slightly relieved,
allowing the rubber to move inward, and a gap
appears.

Axle Bracket
Supplied by
Vehicle
Manufacturer

Gap in rubber of
End Bushing
is normal

PHYSICAL INSPECTION
IF BUSHING MOVEMENT OR LOOSENESS IS NOTED IN THE EQUALIZING BEAM END HUB, DO NOT
OPERATE THE VEHICLE. REPLACE THE RUBBER END BUSHINGS AND ALL CONNECTING PARTS.
THE ABOVE CONDITION CAN RESULT IN COSTLY REPAIR, DOWNTIME, POSSIBLE SEPARATION OF
COMPONENTS, ADVERSE VEHICLE HANDLING, PROPERTY DAMAGE, OR PERSONAL INJURY.

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17

Preventive Maintenance

ULTIMAAX® for Fire and Rescue Vehicles
SERVICE HINT

An equalizing beam end connection that is visibly cleaner than the other connections may indicate a loose connection.
2. If bushing movement or looseness is detected in the equalizing beam end hub, DO NOT operate vehicle. Replace the equalizing beam end bushings and all connecting parts. Refer to the
Component Replacement Section of this publication.
3. Check and record torque values, see Figure 6-9. Correct torque values as required making
sure all fasteners are tightened to 125 foot pounds + 90° rotation or 700 ± 50 foot pounds
torque.
FIGURE 6-9

BAR PIN END BUSHINGS

FIGURE 6-10
Shim Type Bar Pin End Bushing

VISUAL INSPECTION

Contact Area

An indication that the bar pin end bushing requires
replacement is when one or more of the following
conditions apply:
■■ If the contact area, see Figure 6-10 (the flat face

Bolt Hole
Bore

area where bar pin contacts the axle bracket)
reveal signs of excessive wear. Replace if bar pin
thickness measures less than 17⁄8" (47.59 mm).

Confinement
Washer

■■ If bar pin bolt holes bores reveal signs of elonga-

tion or wear, see Figure 6-10.

BAR PIN SHIMS
An indication that the bar pin shims require
replacement is when one or more of the following
conditions apply:

Bar Pin
1.874"
(47.59 mm)
If bar pin measurement is less than
1.874" (47.59 mm), replacement is required.

■■ Visual inspection of contact area on the shim reveals signs of excessive wear.
■■ The thickness of any single leg on the shim, is less than the measurement shown in

Figure 6-11, replacement of bar pin shim is required.

FIGURE 6-11
Original
Thickness
of Shim Leg

Minimum
Thickness
Required

Part Number

1

⁄8" (3.2 mm)

0.123" (3.1 mm)

50131-000

3

⁄16" (4.8 mm)

0.186" (4.7 mm)

50130-000

¼" (6.4 mm)

0.248" (6.3 mm)

50131-000

⁄8" (9.5 mm)

0.371" (9.4 mm)

57026-000

3

Preventive Maintenance

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17730-299

ULTIMAAX® for Fire and Rescue Vehicles
BEAM END AXLE BRACKETS
NOTE

The axle brackets are furnished and welded into position by the vehicle manufacturer or axle
manufacturer.

VISUAL INSPECTION
When inspecting the equalizing beam end connection also inspect the axle brackets for damage
or cracks, see Figures 6-12, 6-13 and 6-14. Any axle bracket that is found damaged or cracked
must be repaired or replaced.
Consult the axle and/or vehicle manufacturer for additional inspections, component repair and
replacement instructions.

PHYSICAL INSPECTION
■■

Bar Pin Style
a. Inspect the axle brackets for damage or cracks in the locations shown in Figures 6-12 and
6-13. Any axle bracket that is found damaged or cracked must be repaired or replaced.
b. Measure the distance between the axle bracket legs for correct width, refer to Figures
6-12 and 6-13 for measurement location and dimensions. An axle bracket outside of the
measurement range must be repaired or replaced.
c. Consult the vehicle manufacturer for inspection, component repair and replacement
instructions

FIGURE 6-12

FIGURE 6-13

Typical location
of crack areas

Look for cracks
in these locations

2.29" ± 0.025"
(58.11 mm ± 0.63 mm)

■■

8.5" ± 0.1"
(216 mm ± 2.6 mm)

NOTE: Typical axle
brackets shown

Adapter Style

FIGURE 6-14

a. Inspect the 2½" (64 mm)
diameter holes in each of the
axle bracket legs, Figure 6-14.
b. Remove any burrs or material
left there by the old adapters.
c. Use a new adapter style bushing as a gauge for fit, being
sure it enters the holes from
the outside of each bracket leg.

ADAPTER STYLE AXLE
Axle
*Standard
Axle Bracket
(Rubber Bushing)
2½" (64 mm)
Axle Bracket Leg
*Typical axle bracket shown

6.01/6.02"
(152.6/152.8 mm)

d. M e a s u r e t h e d i s t a n c e
between the axle bracket legs for correct width, refer to Figure 6-14 for measurement
location and dimensions. The dimension between the inside surfaces of the axle bracket
legs is 6.015" ± 0.005" (152.7 mm ± 0.1 mm), see Figure 6‑14.

17730-299

19

Preventive Maintenance

ULTIMAAX® for Fire and Rescue Vehicles
FRAME HANGER ASSEMBLY
The following points are for guidance and intended to assist personnel in determining when
frame hanger assembly maintenance is necessary.

INSPECTION
■■ Inspect the frame hanger for any damage, cracks or signs of adverse or abrasive contact with

other components. Some minor wear will be evident where the progressive load spring contacts the frame hanger assembly, see Figure 6-15. If more than half the thickness of the frame
hanger plate is damaged or cracked, replace the frame hanger assembly.

■■ Look for wear in the frame hanger cavity due to contact with the jounce stop, see Figure 6-15.

If more than half the thickness of the frame hanger plate is worn or damaged, replace the
frame hanger.

■■ Inspect frame hanger attaching fasteners and frame hanger assembly for signs of looseness

or movement. Retighten any loose fasteners to specified torque. Components damaged by
loose fasteners must be replaced.

FIGURE 6-15
ULTIMAAX 63K Shown

Minor wear area between the
frame hanger plate and
progressive load spring

Jounce Stops

Location of
frame hanger
attaching fasteners

Frame Hanger

Wear area between
the frame hanger plate
and jounce stops

Progressive
Load Spring
Saddle
Assembly

SHEAR SPRINGS
INSPECTION
Inspection of the shear spring should always be conducted with the vehicle in the UNLOADED
condition.
■■ Bent or burred edges on the rate plates extending beyond the rubber are acceptable provided

the rubber can freely expand during vehicle operation, see Figure 6-16.

■■ Creases formed by folding of the rubber surface under load are acceptable. These appear as

stripes on the surface, polished by wear or covered with tacky (sticky) rubber, see Figure 6-17.

FIGURE 6-16
Shear Spring
Flange Flat Side

FIGURE 6-17
Notch on Top

Notch on Top

Shear Spring
Rate Plate

Shear Spring
Angled Side

Preventive Maintenance

Polished Appearance — Creases formed by
the folding of the rubber surface under load
are acceptable.

20

17730-299

ULTIMAAX® for Fire and Rescue Vehicles
FIGURE 6-18
■■ Bonding separation of the rubber from any of the

bonded rate plate surfaces to a maximum depth
of approximately 2" (50 mm) is acceptable, see
Figure 6‑18. If the bonding separation depth is
2" (50 mm) or more, the shear springs require
replacement.

■■ A certain amount of gradual breakup of the rubber sur-

face is acceptable. Use a feeler gauge to measure cuts
or splits in the rubber. If the measurement is over a
depth of 2" (50 mm), then the shear springs require replacement, see Figures 6-19 and 6-20.

FIGURE 6-19

FIGURE 6-20

FIGURE 6-21

PROGRESSIVE LOAD SPRINGS (PLS)
NOTE

Hendrickson Lit. No. 48422-592 – ULTIMAAX Gauge
Card (Figure 6-21) can be used to measure in the
unloaded condition the height of the progressive load
spring (PLS), plus the length of cuts / splits and depth of
separation of the shear spring and the PLS.
Visually inspect the progressive load springs at
regular preventive maintenance intervals. The following points are for guidance and intended to assist
personnel in determining when progressive load spring
component requires replacement, refer to the Component
Replacement Section of this publication.

NOTE

The Hendrickson ULTIMAAX suspension progressive load
springs must be replaced in pairs (left side pairs or right
side pairs or rear position pairs or front position pairs),
even if only one PLS shows unacceptable conditions.
Replacement of only one PLS can cause uneven wear,
and higher premature wear for the one replaced
■■ Always inspect the progressive load spring with the

vehicle in the UNLOADED condition.

■■ The height of a new PLS is 31⁄16" (78 mm). The PLS requires replacement if the height is below

25⁄16" (59 mm), see Figure 6-22.

17730-299

21

Preventive Maintenance

ULTIMAAX® for Fire and Rescue Vehicles
■■ A bent or cracked mounting base requires PLS replacement.
FIGURE 6-22

Progressive Load Spring (PLS) Height
in the Unloaded Condition
Inspection area
for any cuts,
splits, or bonding
separation

PLS height when new 3.1" (78 mm)
Minimum acceptable height 2.3" (59 mm)

Replacement required if PLS height
is less than 2.3" (59 mm)

Mounting
Base

FIGURE 6-23
■■ If any cuts or splits in the rubber of over 2" (50 mm) in length

Progressive Load Spring

and an average depth of ½" (13 mm), the effected PLS
requires replacement. A certain amount of gradual breakup
of the rubber surface is normal. The most probable areas for
potential cuts, splits, or wear are shown in Figure 6-22 as
“/ / / / / / /.”

■■ The bonding separation depth of the rubber from the PLS

mounting base plate surface (see Figure 6-22) is more than
½" (13 mm), the effected PLS requires replacement.

Polished Appearance — Creases formed by the folding of
the rubber surface under load are acceptable.

■■ Creases formed by folding of the rubber surface under load

are acceptable. These appear as stripes on the surface, polished by wear or covered with tacky rubber, see Figure 6-23.

SADDLE CONNECTION
Visually inspect for any signs of movement or looseness and ensure:
■■ Each saddle is centered on each equalizing beam center bushing.
■■ The center bushing inner metal is fully seated to the saddle.
■■ Saddle cap locknuts are tightened to proper torque as specified in the Torque Specifications

Section of this publication.

Saddle cap fasteners — While tightening the saddle cap fasteners maintain an even gap
between the saddle and saddle cap, see Figure 6-24.
NOTE

Tightening the saddle cap fasteners properly will help prevent wear of mating components.
FIGURE 6-24

Preventive Maintenance

22

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ULTIMAAX® for Fire and Rescue Vehicles
CROSS TUBE
The ULTIMAAX cross tube connects the two (2) equalizing beams through the equalizing beam’s
center bushings, see Figure 6-25. The cross tube has clearance to float side-to-side in the center
bushings.
The length of the cross tube will allow side-to-side movement of approximately 23⁄8" (60 mm). For
this reason, the cross tube may appear polished or missing paint at each end where it enters
into the center bushings. This is normal. Also, the cross tube will rattle in straight position which
is acceptable.
FIGURE 6-25
ULTIMAAX 63K Shown

Cross Tube
DO NOT grease or
use as a jacking point

Center Bushing
DO NOT grease
Equalizing
Beam

IMPROPER JACKING METHODS CAN CAUSE STRUCTURAL DAMAGE WHICH CAN CAUSE ADVERSE
VEHICLE HANDLING, PROPERTY DAMAGE OR SEVERE PERSONAL INJURY AND WILL VOID
HENDRICKSON’S WARRANTY.
■■ DO NOT USE THE SUSPENSION CROSS TUBE AS A JACKING POINT, REFER TO VEHICLE MANUFAC-

TURER FOR PROPER JACKING INSTRUCTIONS.

■■ ACCEPTABLE LIFTING POINTS FOR A VEHICLE AT THE RATED LOAD INCLUDE BUT NOT LIMITED

TO: THE AXLE, EQUALIZING BEAM, AND THE VEHICLE FRAME RAIL. REFER TO THE VEHICLE
MANUFACTURER FOR PROPER JACKING INSTRUCTIONS.

DO NOT grease or lubricate the cross tube or the center bushing and DO NOT use the cross tube
as a jacking point, see Figure 6-25.

VISUAL INSPECTION
■■ Visually inspect the overall condition of the cross tube for dents, dings, or bent condition,

replace as necessary.

NOTE

A bent cross tube may cause misalignment of the axles, which may cause abnormal tire wear.
■■ Use a straight edge to inspect the straightness of the cross tube, replace as necessary.

17730-299

23

Preventive Maintenance

ULTIMAAX® for Fire and Rescue Vehicles
TORQUE RODS
THE ULTIMAAX SUSPENSION INCORPORATES TORQUE RODS FOR VEHICLE STABILITY. IF THESE
COMPONENTS ARE DISCONNECTED OR ARE NON-FUNCTIONAL THE VEHICLE SHOULD NOT BE
OPERATED. FAILURE TO DO SO CAN RESULT IN ADVERSE VEHICLE HANDLING AND POSSIBLE TIRE
CONTACT WITH THE FRAME OR THE SUSPENSION.

Visually inspect torque rod bushings for any torn or shredded rubber, inspect for bent, cracked,
or broken torque rods, and for end hubs with any ­elongated “oval” shape. Any of these conditions
will require component replacement.
Torque rod looseness inspection is necessary per the following method below.
■■ With the vehicle shut down, a lever check can be made with a long pry bar placed under each

rod end and pressure applied.

TORQUE ROD LENGTH
Longitudinal torque rod length is determined by the vehicle manufacturer for optimum driveline angles. The longitudinal torque rods maintain these angles and control acceleration and
brake forces.
Transverse torque rod length is also determined by the vehicle manufacturer to center the axles
under the frame.
■■ If the lateral alignment of the axles is incorrect, it may be necessary to shim the transverse