Saddle Cap
Fasteners

2. Raise and support the drive axles on safety stands.
3. Remove the drive tires from the side of the vehicle being serviced.
4. Remove and discard the M16 or M20 saddle cap fasteners that attach the
saddle assembly to the center bushing, see Figure 8‑2.

Center
Bushing
Saddle Cap

Saddle

5. Raise the vehicle’s frame just enough to create a ½" (13 mm) gap between
the saddle assembly and center bushing. Support the vehicle’s frame at this
height on safety stands.
6. Remove the progressive load springs M10 fasteners and discard, see
Figure 8-4.

7. Remove the progressive load springs.
8. Apply NLGI #2–EP (Extreme Pressure) chassis lubricant to the threaded rod of the Saddle
Disassembly Tool Part No. 66086-113L, see Figure 8-3.
FIGURE 8-3
Saddle Disassembly Tool
Hendrickson Part No.66086-113L

Threaded
Rod Nut

NOTE

FIGURE 8-4
ULTIMAAX 52K Shown

Blocking
Nuts
Apply NLGI #2–EP
(Extreme Pressure) chassis lubricant

Install Saddle Disassembly Tool
on each end of the assembly

Progressive
Load Spring
Fasteners

The threaded rod spacer and spacer nut are designed and orientated to fit into the saddle assembly openings, see Figure 8-5.
9. Install both Saddle Disassembly Tool on each end of one saddle assembly, rotate the threaded
rod blocking nuts until each are oriented properly into the saddle assembly openings, see
Figures 8-4 and 8-5.
FIGURE 8-5

Saddle Assembly
Opening

Threaded Rod
Blocking Nuts

17730-301

Saddle Disassembly Tool
Hendrickson Part No. 66086-113L

35

Component Replacement

ULTIMAAX® for Kenworth Vehicles
SERVICE HINT

Use rachet strap attached to each saddle half and the frame or vehicle body to secure the saddle
halves during removal.
10. Snug the Saddle Disassembly Tool.

NOTE

The shear springs are in each frame hanger are compressed when installed.
11. Remove and discard the M20 saddle fasteners, see Figure 8-6.
12. To separate the two saddle halves, evenly rotate the threaded rod nut to tighten the Saddle
Disassembly Tool, see Figure 8-6.

FIGURE 8-6
ULTIMAAX 52K Shown

Frame Hanger

M10 Flange Bolt

Saddle Assembly Half
(Inboard)

Progressive Load
Spring
Saddle Assembly Half
(Outboard)
M20 Flange Bolt

Saddle Disassembly Tool
Part Number 66086-113L

M10 Flange Locknut
Tightening Torque
30 ± 2 ft. lbs
(41 ± 3 Nm)

Shear Spring
NOTE: During assembly,
it may be necessary to
use tape to hold the shear
spring in position. After
installation is complete
remove tape.

M20 Flange Locknut
Tightening Torque
325 ft. lbs (440 Nm)
PLUS a 90° rotation,
OR 560 ± 30 ft. lbs
(760 ± 40 Nm)

13. Remove the saddle halves and / or shear springs for replacement.
EACH FRAME HANGER ASSEMBLY WEIGHS APPROXIMATELY 165-252 POUNDS (75-114 KILOGRAMS),
USE APPROPRIATE LIFTING DEVICES TO REMOVE OR INSTALL THE FRAME HANGER ASSEMBLY. FAILURE
TO DO SO CAN RESULT IN DAMAGE TO THE VEHICLE OR PERSONAL INJURY.

14. If replacing the frame hanger, remove the frame fasteners per the vehicle manufacturer’s
instructions. Remove frame hanger.

ASSEMBLY
1. If installing a new frame hanger continue to Step 2. If installing or servicing shear springs or
saddle assembly, proceed to Step 3.
EACH FRAME HANGER ASSEMBLY WEIGHS APPROXIMATELY 165-252 POUNDS (75-114 KILOGRAMS),
USE APPROPRIATE LIFTING DEVICES TO REMOVE OR INSTALL THE FRAME HANGER ASSEMBLY. FAILURE
TO DO SO CAN RESULT IN DAMAGE TO THE VEHICLE OR PERSONAL INJURY.

2. Position the frame hanger assembly against the frame rail. Install fastener's per the vehicle
manufacturer’s instructions and specifications.
SERVICE HINT

During assembly, it may be necessary to use tape to hold the shear springs in position. After installation is complete remove tape.
3. Position the shear springs with the flanged flat side against the frame hanger with the shear
spring angled downward, see Figure 8-7.

Component Replacement

36

17730-301

ULTIMAAX® for Kenworth Vehicles
FIGURE 8-7
ULTIMAAX 52K Shown
SHEAR SPRING
Notch
Flange Flat Side
on Top
Notch
on Top

Angled
Side

TOP VIEW

SIDE VIEW

Frame
Hanger

Frame Hanger

Position shear
springs anged
at side against
the frame hanger

Shear Springs
Angled
downward

4. Apply NLGI #2–EP (Extreme Pressure) chassis lubricant to the threaded rod of the
Saddle Assembly Tool Part No. 66086‑108L,
see Figure 8-8.
NOTE

The threaded rod spacer and spacer nut are
designed and orientated to fit into the saddle
assembly openings.
5. Apply P-80 lubricant to the shear spring’s
angled face and to the mating face of the
saddle halves, see Figure 8-9.

Shear Springs
Flanged Flat Side

FIGURE 8-8
Saddle Assembly Tool
Hendrickson Part No. 66086-108L
Apply NLGI #2–EP
Chassis Lubricant
Threaded Rod
Threaded Rod
Threaded Rod
Spacer

Threaded Rod
Spacer Nut

FIGURE 8-9
ULTIMAAX 52K Shown
Saddle Assembly
Half (Inboard)

Shear Spring
face area
Saddle Assembly
Half (Outboard)

Mating face of
Saddle Assembly

Lubrication
Apply P80 lubricant to the angled
face area of the Shear Springs and
mating face of the Saddle Assembly

6. On each side of the saddle assemblies, rotate the threaded rod spacers and spacer nuts of
the saddle assembly tool until each are oriented properly into the saddle assembly openings,
see Figure 8-10.
SERVICE HINT

Use a mechanism to attach to the frame to aid in holding the saddle up while performing procedure (such as a strap or rope) attached to each saddle half and the frame or the vehicle body
to secure the saddle halves during installation or have an additional person assist to align the
saddle halves properly.
7. Position the inner saddle half into the frame hanger along with the shear springs, outer saddle
half, see Figure 8-11.
8. Bring both saddle halves together with the Saddle Assembly Tool. Evenly tightening the Saddle
Assembly Tool until both saddle halves are seated against each other.

17730-301

37

Component Replacement

ULTIMAAX® for Kenworth Vehicles
FIGURE 8-10

Saddle Assembly
Opening

Threaded Rod
Spacer

Saddle Assembly Tool
Hendrickson Part No. 66086-108L
FIGURE 8-11
Saddle half

SADDLE UNCOMPRESSED

Threaded Spacer Nut
Shear Spring

Frame
Hanger
Spacer
Saddle half

SADDLE COMPRESSED

Saddle half

Threaded Rod

Threaded Rod
Threaded Spacer Nut

Frame
Hanger

Shear Spring
Saddle half

9. Install the new M20 saddle fasteners. Tighten in the proper sequence shown in Figure 8-12 to
325 foot pounds plus a 90° rotation, or 560 ± 30 foot pounds torque.
10. Remove temporary tape from the shear springs if used during assembly.
11. Remove the Saddle Assembly Tool.
12. Install the progressive load springs.
13. Install the progressive load spring M10 fasteners. Tighten to

30 ± 2 foot pounds torque.

14. Remove the frame supports.
15. Lower the frame of the vehicle while engaging and centering the saddles on the equalizing
beam’s center bushings, see Figure 8-13.
Component Replacement

38

17730-301

ULTIMAAX® for Kenworth Vehicles
FIGURE 8-12
M20 Flange Locknut
Tightening Torque 325 ft. lbs (440 Nm)
PLUS 90° rotation
OR 560 ± 30 ft. lbs (760 ± 40 Nm)

TORQUE SEQUENCE
Tighten in the proper sequence

M20 Flange
Bolt
M20 Flange
Locknut
Saddle Assembly
Halves

Saddle
Assembly

FIGURE 8-13
Bar Pin Style

Adapter Style
0 mm to 3.5 mm

0 mm to 3.5 mm
Saddle

Saddle
Cross Tube

Cross Tube

End Plug

End Plug

Center Bushing

A SADDLE ASSEMBLY IS ATTACHED TO THE CENTER BUSHING OF EACH EQUALIZING BEAM WITH TWO (2)
SADDLE CAPS. EACH SADDLE CAP USES TWO (2) BOLTS TO CLAMP THE CENTER BUSHING INNER METAL
TO THE SADDLE. EACH SADDLE CAP MUST BE INSTALLED SO THAT THERE IS AN EVEN GAP BETWEEN THE
SADDLE CAP AND THE BASE OF THE SADDLE LEGS AS SHOWN IN FIGURE 8-14. IF EACH SADDLE CAP IS
NOT INSTALLED EVENLY,THE SADDLE LEGS COULD BECOME DEFORMED, RESULTING IN BENT BOLTS OR
DAMAGED SADDLES.

NOTE

Tightening the saddle cap fasteners properly will help prevent wear of mating components, such
as the beam center bushing, saddle, and saddle cap.
16. While tightening the saddle cap fasteners, maintain an even gap between the saddle and
saddle cap, see Figure 8-14.
FIGURE 8-14

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

17730-301

Center Bushing

39

Component Replacement

ULTIMAAX® for Kenworth Vehicles
FIGURE 8-15

17. Install the saddle cap fasteners and tighten evenly in several steps in
proper sequence to achieve uniform bolt tension, see Figure 8-15:
■■

46K • 52K Capacity –

200 ± 20 foot pounds torque

■■

60K • 70K Capacity –

558 ± 32 foot pounds torque

18. Install the tires.
19. Remove supports from the axles and lower the vehicle onto the ground.
20. Remove the wheel chocks.

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

DISASSEMBLY
1. Chock the front wheels of the vehicle.
2. Raise the vehicle’s frame until the saddle assembly contacts the bottom of the frame hanger
assembly. Support the vehicle’s frame at this height with safety stands.
3. Remove and discard the M10 fasteners that attach the progressive load springs to the saddle
assembly.
4. Remove the progressive load springs from the frame hanger assembly.

ASSEMBLY
1. Install the progressive load springs into the frame hanger assembly.
2. Install four M10 flange bolts that attach the PLS to the saddle assembly. The flange bolts must
be installed with the locknuts facing downward as shown in Figure 8-16.
3. Tighten the PLS fasteners to

30 ± 2 foot pounds torque.

4. Remove the frame safety stands and lower the vehicle.
5. Remove the wheel chocks.
FIGURE 8-16

ULTIMAAX 52K Shown

Progressive
Load Spring (PLS)

M10 Flange Locknut
Tightening Torque
30 ± 2 ft. lbs (41 ± 3 Nm)

Frame Hanger
Saddle

Component Replacement

40

17730-301

ULTIMAAX® for Kenworth Vehicles
EQUALIZING BEAM
DISASSEMBLY
1. Chock the wheels of the steer axle.
2. Raise and support the drive axles with safety stands.
3. Remove the tires.
4. Support the pinion angle of the drive axles to prevent axle movement during service.
5. Remove the saddle cap bolts from both inboard and outboard side of each equalizing beam.
6. Remove the saddle caps, see Figure 8-17.
FIGURE 8-17

ULTIMAAX 52K Shown
Frame Hanger

Equalizing Beam
End Bushing

M16 Locknut
Tightening Torque
200 ± 20 ft. lbs
(270 ± 30 Nm)

Saddle

M20 Flange Fasteners
Tightening Torque
325 ft. lbs (440 Nm)
+ 90° Rotation
or 560 ± 30 ft. lbs.
(760 ± 40 Nm)

Equalizing Beam
Assembly
Equalizing Beam
Center Bushing

End Plug
NOTE:
Ensure center bushing end plug
is located on the outboard side
of the equalizing beam assembly
prior to installation

Saddle Cap

M16 Flange Bolt

7. Raise the vehicle’s frame just enough to create a ½" (13 mm) gap between the saddles and
the center bushings. Support the vehicle’s frame at this height with safety stands.
THE WEIGHT OF THE EQUALIZING BEAM ASSEMBLY IS APPROXIMATELY 290 TO 315 POUNDS (131
TO 141 KILOGRAMS). PRIOR TO REMOVING THE END BUSHING BOLTS FROM THE EQUALIZING BEAM,
SUPPORT THE END OF THE EQUALIZING BEAM TO PREVENT IT FROM DROPPING. CARE SHOULD BE
TAKEN AT REMOVAL AND INSTALLATION TO PREVENT PERSONAL INJURY OR DAMAGE TO COMPONENTS.

8. Support both equalizing beams under the center bushing with floor jacks.
9. Adapter Style End Bushing – Proceed to Step 11.
NOTE

Prior to disassembly of the equalizing beam bar pin fasteners, note the orientation of the bar pin
alignment shims, see Figure 8-18. It is required that the bar pin alignment shims are installed
in the same orientation and location as removed to preserve the existing vehicle alignment.
Improper vehicle alignment can increase tire wear.
10. Bar Pin Style End Bushing – Note the orientation and location of the bar pin shims, see
Figure 8-18.
11. Remove and discard end bushing fasteners.

SERVICE HINT

17730-301

The center bushing will allow the cross tube and the equalizing beam to angle downward once
the equalizing beam end fasteners are removed.
41

Component Replacement

ULTIMAAX® for Kenworth Vehicles

12. Slowly lower the floor jacks and
remove the equalizing beams from
the axle brackets.
PRIOR TO REMOVING BOTH EQUALIZING
BEAMS, SUPPORT THE PINION OF EACH
DRIVE AXLE. FAILURE TO DO SO CAN
RESULT IN PERSONAL INJURY OR ALLOW
THE AXLES TO SHIFT MAKING REASSEMBLY
MORE DIFFICULT.

13. Slide the equalizing beams off the
cross tube and out from under the
vehicle.
14. Remove the floor jacks from under
the equalizing beams.

FIGURE 8-18
ULTIMAAX
46K • 52K Shown
1" Locknut
Tightening Torque
525 ± 75 ft. lbs
(712 ± 102 Nm)

Axle Bracket
Supplied by
Manufacturer

Bar Pin