PI-0827

Service Program
Trucks
Mack Trucks, Inc.
Greensboro, NC USA
Date
Group
No.
Release
Page
8.2013
722
002
1
1(32)
SB-10054290-9105
Top Plate and Spring Seat, Replacement
CHU, CXU
PI0827, Top Plate and Spring Seat, Replacement
(August 2013)
Note: Information is subject to change without notice.
Illustrations are used for reference only and may differ slightly from the actual vehicle being
serviced. However, key components addressed in this information are represented as
accurately as possible.
A number of Pre Production vehicles have been built equipped with the Twin Y Air
Suspension. Upon review of these vehicles it has been determined that some have defective
bushings within the top plate and spring seat. To address the defective bushings, this bulletin
as been created which covers parts involved (Table 1 and Figure 1) , a procedure for
inspection and a procedure for replacement of the top plate and spring seat, if replacement is
found necessary.
PV729-PI0827
USA60163
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
Table 1 contains a complete list of service parts that may be required to the fix the bushing
problem. Figure 1 shows the location of the these parts.
Service Parts (Table 1)
Part Number
Description
Quantity
21799969
Top Plate (LH)
1 per Wheel
21799970
Top Plate (RH)
1 per Wheel
21947030
Spring Seat (LH)
1 per Wheel
21947031
Spring Seat (RH)
1 per Wheel
21759985
Service U Bolts
2 per Wheel
947971
U Bolt Fasteners
4 per Wheel
995681
Y Blade to Seat Fasteners
(M18)
4 per Wheel
22035866
Y Blade to Seat Fasteners
(Nuts)
4 per Wheel
22039810
Y Blade to Seat Fasteners
(Spring Washer)
4 per Wheel
990861
S Cam Tube Support
Bracket Fastener
1 per Wheel
996522
Set Screw for Pressure
Plate
1 per Wheel
Page
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Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
W7083166
Figure 1 Location of Service Parts
1 — Y Blade (Shown for reference only not listed as a replacement part)
2 — Top Plate (Shown in table 1 as LH and RH)
3 — Spring Seat (Shown in table 1 as LH and RH)
4 — Service U bolts
5 — Fasteners for Service U bolts
6 — Bushing within Y blade at hanger bracket (Shown for reference only not listed as a
replacement part)
7 — Fasteners for Top Plate and Spring Seat (M18)
8 — Fasteners for Top Plate and Spring Seat (Nuts)
9 — Fasteners for Top Plate and Spring Seat (Spring Washers)
10 — Pressure Plate (Shown for reference only not listed as a replacement part)
11 — Set Screw for Pressure Plate
12 — Spring Seat Bushings (If bushings are found defective the Spring Seat will be replaced
which includes new bushings)
13 — Top Plate Bushings (If bushings are found defective the Top Plate will be replaced
which includes new bushings)
Page
3(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
Inspection Procedure
TWIN Y AIR SUSPENSION BUSHING INSPECTION
1. Visual inspection, do the Y blades make contact with the outer shell of the bushing? See
figures for pass or fail. If passes, continue with Step 2. If fails, proceed to the Top Plate and
Spring Seat, Replacement procedure on page 7.
W7083167
PASS
W7083168
FAIL
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Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
2. Measure the distance between the Y blades as close as possible to top plate and spring
seat (dimension A). If the distance is less than 64.7 mm (2.55 in) it fails. If fails, proceed to the
Top Plate and Spring Seat, Replacement procedure on page 7. If test passes, continue with
Step 3.
W7083170
Page
5(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
3. Check torque on top plate and spring seat fasteners with torque wrench set to
135 Nm (100 ft-lb). If the torque wrench moves more than approximately 10 degrees the test
fails. If test fails, proceed to the Top Plate and Spring Seat, Replacement procedure on
page 7. If test passes, continue with Step 4.
W7083169
4. Check torque on top plate and spring seat fasteners with torque wrench set to
271 Nm (200 ft-lb). If the torque wrench moves more than approximately 10 degrees the test
fails. If test fails, proceed to the Top Plate and Spring Seat, Replacement procedure on
page 7. If test passes, continue with Step 5.
5. Check torque on top plate and spring seat fasteners with torque wrench set to
407 Nm (300 ft-lb). If the torque wrench moves more than approximately 10 degrees the test
fails. If test fails, proceed to the Top Plate and Spring Seat, Replacement procedure on
page 7.
Note: If the bushings pass this final torque test, the bushings are not defective and the
procedure is complete and no further action will be required.
Page
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Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
Top Plate and Spring Seat, Replacement
REMOVAL
1. Park the vehicle on a flat level surface. Place the shift lever in neutral. Apply the parking
brake. Chock the front wheels.
2. Disconnect all cables from the negative (ground) battery terminals to prevent personal
injury from electrical shock and prevent damage to electrical components.
3.
DANGER
Failure to properly support the front of the axle housing may result in the axle rolling
forward, causing serious injury or death.
Following safe lifting guidelines, lift and support both the frame and the axle housing.
4. Remove the wheels and tires.
5. Release the parking brake.
6. Cage the brake chamber.
7. Back-off the brake slack adjuster so that the brake drum can be removed.
8. Remove the brake drum.
W5072399
Page
7(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
9. Remove the brake shoes.
W7072862
Hub Removed For Illustration Purpose Only
10.
CAUTION
The weight of the axle housing is not distributed evenly. Make sure the jack can safely
support the axle housing before removing the trailing blade bolts. If the axle housing is not
supported properly, the housing can fall off the jack and result in component damage.
Before loosening the trailing blade fastener (left side), mark the adjusting washers for reinstallation.
Loosen the fastener securing the trailing blade to the hanger bracket (right side).
Note: Use care when loosening the trailing blade fastener, so that the fastener is not
damaged.
Page
8(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
W6072195
Left Side Shown
W7072863
Right Side Shown
Group
No.
Release
722
002
1
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Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
11. With assistance, remove the fasteners securing the trailing blade to the top plate and
spring seat on the axle. Discard the fasteners.
W7068413
Hub Removed For Illustration Purpose Only
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Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
12. Remove the previously-loosened trailing blade fastener at the frame hanger bracket.
W7068414
13. Remove the trailing blade from the axle and the frame hanger bracket.
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11(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
14. Remove the fasteners securing shock absorbers to the mounting brackets. Remove the
shock absorbers.
Note: While removing the shock absorbers, pay close attention to the mounting location on
the upper mounting bracket for proper re-installation.
W7068435
W7068619
Page
12(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
15. Remove the fasteners that attach the S-cam tube support bracket to the top plate. Loosen
the U-bolt on the S-cam tube to allow clearance for removal of the top plate.
16. Using the dash mounted rear suspension air dump switch, release the air in the rear air
spring or disconnect the leveling rod from the leveling valve so that the pressure is released
from the air springs.
W6079166
MACK Fab Axle Shown
17. Remove the air spring fastener securing the air spring to the spring seat.
W6080097
1 — Fastener Attaching Air Spring to Spring Seat
Page
13(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
18. Loosen the set screw in the spring seat that secures the pressure plate against the axle
housing.
W6079167
Page
14(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
19.
CAUTION
To avoid component damage support the spring seat when removing the U-bolts. The
spring seat may separate from the axle housing and fall.
Remove the U-bolts securing the top plate and spring seat to the axle housing.
Note: Some applications maybe equipped with HuckR type fasteners and require using a
removal tool.
W7072409
Hub Removed For Illustration Purpose Only
Page
15(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
20. Remove the top plate and spring seat. Remove the set screw and pressure plate from the
spring seat.
W7079173
1 — Pressure Plate
2 — Set Screw
21. For top plate and spring seat removal on the left side of the axle, repeat Steps 4 through
20.
Note: Before loosening the left side trailing blade fasteners, mark the adjusting washers for
re-installation.
Page
16(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
INSTALLATION
1. With assistance, install the top plate and spring seat onto the axle housing using new Ubolts and fasteners.
Hand tighten U-bolt fasteners so that the spring seat is against the bottom of the axle (do not
overtighten).
Note: Before tightening the U-bolts, make sure the axle guide pins are properly positioned in
the hole in the top plate.
W7080093
1 — U-Bolt Fasteners
2 — U-Bolts
3 — Top Plate
4 — Spring Seat
Page
17(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
2. Assemble pressure plate and set screw on the spring seat (both sides), do not tighten at
this time.
Note: While installing the pressure plate to the spring seat make sure that the spring seat is
touching the vertical wall and lower surface of the axle housing.
W7081619
1 — Alignment Area
Page
18(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
3. Hand tighten the set screw attaching the pressure plate.
Note: This is needed to keep the spring seat in position while tightening the U-bolts.
W6079168
1 — Set Screw
2 — Pressure Plate
4. Gradually tighten the U-bolt fasteners in increments using the X-pattern shown until each is
finally tightened to 540 ± 75 Nm (400 ± 55 ft-lb).
W7076443
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Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
5. Tighten the set screw attaching the pressure plate to the spring seat to
70 ± 12 Nm (50 ± 9 ft-lb).
Note: If applicable, cut or shorten the U-Bolts approximately one inch past the end of the nut.
6. Install the fasteners securing the S-cam tube support bracket to the top plate. Tighten the
fasteners to 60 ± 10 Nm (44 ± 7 ft-lb). Tighten the U-bolt fasteners on the S-cam tube to
40 ± 6 Nm (29 ± 4 ft-lb).
7. Position the trailing blade onto the vehicle.
W7068414
8. Install new fasteners securing the trailing blade to the top plate and spring seat on the axle.
Do not tighten the fasteners.
W7080092
Hub Removed For Illustration Purpose Only
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20(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
9. Position the opposite end of the trailing blade onto the frame hanger bracket. Loosely
attach with the bolt, cam adjustment washers (left-hand side) and spacer adjustment washers
(right-hand side).
Note: Do not tighten the fasteners at the frame hanger until the vehicle is at the correct ride
height.
W7068412
10. Tighten the fasteners securing the trailing blade to the axle (top plate and spring seat) to
475 ± 50 Nm (350 ± 37 ft-lb).
Note: Wait one minute after torquing the fasteners, then re-torque them to the same value.
Note: Do not tighten the fastener at the frame hanger bracket until the vehicle is at the correct
ride height.
Page
21(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
11. Align the air spring stud in the spring seat and attach it using the fastener. Tighten the
fastener to 70 ± 10 Nm (50 ± 7 ft-lb).
W6080097
1 — Fastener Attaching Air Spring to Spring Seat
12. Connect leveling rod to the axle housing.
W6079166
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22(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
13. Loosely attach the shock absorber to the vehicle using the shock mounting fasteners.
Note: While re-installing the shock absorber onto the upper mounting bracket be sure to
attach it in the location where previously removed.
Note: Do not tighten the shock mounting fasteners until the vehicle is at the correct ride
height.
W7068435
W7068619
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Mack Trucks, Inc.
Service Program
Date
8.2013
14. Install the brake shoes.
W7072862
Hub Removed For Illustration Purpose Only
15. Install the brake drum.
W5072399
Group
No.
Release
722
002
1
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Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
16. Install the wheels and tires and tighten fasteners securely.
Note: Final torque should be done after vehicle is lowered and park brake is set.
17. For top plate and spring seat installation on the left side of the axle, repeat Steps 1
through 15.
Note: Before loosening the left side trailing blade fasteners, mark the adjusting washers for
re-installation.
18. Reconnect all previously removed cables to the negative (ground) battery terminals.
19. Start the engine and fill the air system to proper operating pressure (120 psi [8 kPa]), so
that the brakes can be adjusted properly. Once the proper operating pressure is reached turn
off the engine.
Note: Make sure the park brake is released.
20. Uncage the brake chambers.
21. Adjust brakes to specifications, refer to the brake manufacturer’s specifications for this
procedure
22. Remove jack stands and jack from under the vehicle.
23.
DANGER
Stay clear when suspension air is released. Chassis may drop quickly, which can cause
serious injury or death to anyone under the vehicle.
DANGER
Use caution when moving the load leveling valve arm down. This will release the
suspension air and the chassis may drop quickly, possibly causing serious injury or death
to anyone under the vehicle.
Release the air in the rear air springs by using the dash mounted rear suspension air switch
or disconnect the leveling rod from the leveling valve at the differential. Move the valve lever
so that the air springs are deflated.
Page
25(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
W6079166
MACK Fab Axle Shown
24. Fill the rear air springs by using the dash mounted rear suspension air switch or reconnect leveling rod to the leveling valve.
Note: Ensure that the air system is at normal operating pressure (120 psi [8 kPa]).
25. Check the ride height, refer to Air Suspension Ride Height Check/Adjustment procedure
on page 29.
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Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
26. Align the previously made marks on the alignment washers (left side only).
Note: This should assist in getting close to the proper alignment.
Note: After a suspension component replacement an alignment should be performed.
W6072195
Left Side Shown
27. With vehicle at correct ride height, tighten fastener at the frame hanger bracket to
675 ± 67 Nm (500 ± 50 ft-lb).
W7072863
Right Side Shown
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27(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
28. With vehicle at correct ride height, tighten the upper and lower shock absorber mounting
fasteners to 220 ± 35 Nm (160 ± 25 ft-lb).
29. Apply the parking brake.
30. Tighten the wheel fasteners to 645 ± 35 Nm (475 ± 25 ft-lb).
31. Remove the wheel chocks.
32. After a suspension component replacement an alignment should be performed.
33. Road-test the vehicle for 10 miles to seat components, then follow the procedure in
installation Step 4 to re-tighten the U-bolt fasteners.
Page
28(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
Air Suspension Ride Height Check/Adjustment
Prepare the vehicle for ride height calculation as follows:
1. Park the vehicle on a level surface (the front wheels must be pointed straight ahead).
2. Free and center all suspension joints by slowly moving the vehicle back and forth twice
without using the brake. When coming to a complete stop, make sure the brakes (parking and
service) are released.
3. Chock the front wheels.
Note: Measurements must be performed on an unloaded vehicle.
4. Check all tires for proper inflation. Adjust tire air pressure to tire manufacturer’s
specifications.
5. Using the dash mounted rear suspension air dump switch release the air in the rear air
spring, or disconnect the leveling rod from the leveling valve so that the pressure is released
from the air springs.
WARNING
Avoid personal injury. BEFORE releasing air pressure from air springs, BE SURE neither
your hand nor another persons hand, etc., is in a position where it could be pinched
between components when the frame/suspension drops.
6. Start the engine and allow the air system to attain normal operating pressure of
827 kPa (120 psi). Turn off the engine.
7. Fill the rear air springs with air using the dash mounted switch or reconnect the actuator
rod to the load leveling valve lever.
Ensure the air system is at normal operating pressure of 827 kPa (120 psi).
8. Measure the size of the frame.
Note: The ride height measurement is dependent on frame size.
Note: Figure 1 shows an image of frame types with measurements from top of frame to frame
mounting bracket.
9. Measure the distance from the floor to the center of the axle.
10. Measure the distance from the bottom edge of the frame to the floor, using special tool
9992870.
11. The difference in the two measurements is the ride height. Verify that the vehicle is at the
correct ride height.
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Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
12. Adjust the ride height (if required).
W7081225
13. Loosen the fastener securing the load leveling valve to the frame. Use the ride height
adjustment socket wrench J-44544 to adjust the valve so the ride height is within
specification. The suspension ride height is changed by turning the load leveling valve
clockwise (to raise) or counter-clockwise (to lower). Tighten the fastener securing the load
leveling valve to the frame to 175 ± 40 Nm (129 ± 30 ft-lb).
14. Re-check the ride height to confirm the accuracy of the leveling valve adjustments
15. Using the dash mounted rear suspension air dump switch release the air in the rear air
spring, or disconnect the leveling rod from the leveling valve so that the pressure is released
from the air springs.
WARNING
Avoid personal injury. BEFORE releasing air pressure from air springs, BE SURE neither
your hand nor another persons hand, etc., is in a position where it could be pinched
between components when the frame/suspension drops.
16. Start the engine and allow the air system to attain normal operating pressure of
827 kPa (120 psi). Turn off the engine.
17. Fill the rear air springs with air using the dash mounted switch or reconnect the actuator
rod to the load leveling valve lever.
Ensure the air system is at normal operating pressure of 827 kPa (120 psi).
18. Re-check the ride height.
If the ride height measurement is not within the specifications. Check the leveling valve and
other suspension components for wear of damage.
19. Apply the parking brake.
20. Remove the wheel chocks.
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30(32)
Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
Frame and Ride Height Specifications
Table A — Frame Height and Ride Height Measurements
Frame Height mm (in.) including frame type
Ride Height mm. (in.) (unloaded)
266 (10.47)
210 ± 5 (mm), 8.27 ± .2 (in)
300 (11.81)
193 ± 5 (mm), 7.6 ± .2 (in)
W7081729
1 = 103 mm (for 266 frame height)
and 120 mm (for 300 frame height)
Figure 1
Ride Height Adjustment
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Mack Trucks, Inc.
Service Program
Date
8.2013
Group
No.
Release
722
002
1
Reimbursement
This repair is covered by an authorized Service Program. Reimbursement is
obtained via the normal claim handling process.
Claim Type (used only when uploading from the Dealer Bus.
Sys.)
B
Recall Status
Vehicle inspected, repair not required
1- Inspected OK
Vehicle repaired per instruction
2- Modified per
instruction
Labor Code
Primary Labor Code
Labor Code Inspection (only) complete vehicle
1361C-01–96
2.0 hrs.
Labor Code Repair each wheel end
1361D-01–96
3.1 hrs.
Time to take charge and determine campaign status
17003–0–01 —
0.3 hrs.
Causal Part
85003025
Parts Disposition
Authorization Number
Expiration Date
>
Note: Take Charge Time is not included in the Labor Code for this operation. Take charge
may be eligible but can only be used once per repair visit. If vehicle is having other warranty
repairs performed, take charge should be charged to the warranty repair, otherwise take
charge can be charged to this service program.
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