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

Preventive Maintenance

18

Adapter
Flat Side
Vertical

17730-301

ULTIMAAX® for Kenworth Vehicles
JACK TEST
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.
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.

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
Equalizing Beam

Cotter Pin

ULTIMAAX 60K • 70K Shown

17/8" Slotted Nut
7

1 /8" Slotted Nut
Tightening Torque
125 ft. lbs. (170 Nm)
+ 90° rotation or
700 ± 50 ft. lbs. (949 ± 68 Nm)

17730-301

Beam End Adapter
Beam End Shaft
Beam End Adapter

19

Adapter Style
End Bushing

Preventive Maintenance

ULTIMAAX® for Kenworth Vehicles
BAR PIN STYLE END BUSHINGS – ULTIMAAX 46K•52K
FIGURE 6-10
Shim Type Bar Pin End Bushing

VISUAL INSPECTION

Contact Area

An indication that the 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 – ULTIMAAX 46K•52K
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

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 – ULTIMAAX 46K•52K
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.

Preventive Maintenance

20

17730-301

ULTIMAAX® for Kenworth Vehicles
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.
■■

Adapter Style – ULTIMAAX 60K•70K
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.
d. Measure the distance 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.

FIGURE 6-12

FIGURE 6-13
BAR PIN STYLE AXLE
ULTIMAAX 46K • 52K

FIGURE 6-14
ADAPTER STYLE AXLE
ULTIMAAX 60K • 70K

Typical
location
of crack
areas

Look for cracks
in these
locations

*Standard
Axle Bracket
(Rubber
Bushing)

2½"
(64 mm)

Axle Bracket
Leg
2.29" ± 0.025"
(58.11 mm ± 0.63 mm)

8.5" ± 0.1"
(216 mm ± 2.6 mm)

6.01/6.02"
(152.6/152.8 mm)

NOTE: Typical axle brackets shown

FRAME HANGER ASSEMBLY
The following points are for guidance and intended to assist personnel in determining when
frame hanger assembly maintenance is necessary.
FIGURE 6-15
ULTIMAAX 52K Shown

Jounce Stops

Minor wear area between the
frame hanger plate and
progressive load spring
Location of
frame hanger
attaching fasteners

Frame
Hanger

Progressive
Load Spring

Wear area between
the frame hanger plate
and jounce stops
Saddle
Assembly

17730-301

21

Preventive Maintenance

ULTIMAAX® for Kenworth Vehicles
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 the frame hanger attaching fasteners and frame hanger assembly for signs of loose-

ness or movement. Re-tighten any loose fasteners to specified torque. Components damaged
by loose fasteners must be replaced.

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 pro-

vided 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

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

Preventive Maintenance

22

17730-301

ULTIMAAX® for Kenworth Vehicles
FIGURE 6-19

FIGURE 6-20

PROGRESSIVE LOAD SPRINGS (PLS)
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 (1) PLS can cause uneven wear, and
higher premature wear for the one replaced.
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.

SERVICE HINT

Use Hendrickson gauge card (Lit. No. 48422‑592 for 48K•52K) or (Lit. No. 48422‑578 for
60K•70K) in unloaded condition to help determine the height, length of cut or split and depth of
separation of the ULTIMAAX progressive load spring (PLS), see Figure 6-21.
FIGURE 6-21

17730-301

23

Preventive Maintenance

ULTIMAAX® for Kenworth Vehicles
Always inspect the progressive load spring with the vehicle in the UNLOADED condition.
■■ The height of a new PLS is:

48K•52K – 31⁄16" (78 mm) • 60K•70K – 27⁄8" (73 mm)
■■ The PLS requires replacement if the height is below, see Figure 6-22:

48K•52K – 25⁄16" (59 mm) • 60K•70K – 23⁄16" (55 mm)
FIGURE 6-22
Progressive Load Spring (PLS) Height in Unloaded Condition
NEW

MINIMUM

46K • 52K

3.1" (78 mm)

2.3" (59 mm)

Inspection area for any
cuts, splits, or
bonding separation

60K • 70K

2.9" (73 mm)

2.2" (55 mm)

Mounting Base

FIGURE 6-23
■■ A bent or cracked mounting base

requires PLS replacement.

■■ If any cuts or splits in the rubber

of over 2" (50 mm) in length 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 likely areas for
potential cuts, splits, or wear are
shown in Figure 6-22 as “/ / / / / / /.”

■■ If any bonding separation depth of

Progressive Load Spring

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

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

■■ 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
FIGURE 6-24

Saddle

Saddle Cap Locknut
M16,Tightening Torque M20,Tightening Torque
558 ± 32 ft. lbs.
200 ± 20 ft. lbs.
(757 ± 43 Nm)
(270 ± 30 Nm)

Maintain an
even gap
between
the saddle and
the saddle cap
Equalizing
Beam
Saddle Cap

Center Bushing

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 full seated to the saddle.

Preventive Maintenance

24

17730-301

ULTIMAAX® for Kenworth Vehicles
■■ 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.

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 2½" (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.
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

MANUFACTURER FOR PROPER JACKING INSTRUCTIONS.

■■ ACCEPTABLE LIFTING POINTS FOR A VEHICLE AT THE RATED LOAD INCLUDE BUT ARE 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.
FIGURE 6-25
ULTIMAAX 52K Shown

Center Bushing
DO NOT grease
Equalizing Beam

Cross Tube
DO NOT grease or use
as a jacking point

VISUAL INSPECTION
NOTE

A bent cross tube may cause misalignment of the axles, which may cause abnormal tire wear.
■■ Visually inspect the overall condition of the cross tube for dents, dings, or bent condition,

replace as necessary.

■■ Use a straight edge to inspect the straightness of the cross tube, replace as necessary

17730-301

25