FSB 722-005A

Mack Trucks, Inc.
Greensboro, NC USA
Field Service Bulletin
Trucks
Date
Group
No.
Release
Page
10.2015
722
005
01
1(32)
Twin-Y Suspension, Trailing Blade,
Replacement
CHU, CXU, CSM, CMM
(MACK Axles)
FSB 722-005, Twin Y Suspension, Trailing Blade,
Replacement
Mack Axles
(October 2015)
Some MACK CHU, CXU, CSM, and CMM trucks built 06/13/2013 through 09/25/2015 and
equipped with Twin-Y suspension may require replacement of the Twin-Y trailing blades with
a more robust design. The new Twin-Y trailing blades have a new profile with a stronger
material thickness of 7.0 mm (0.28 in). All four trailing blades will require replacement in this
repair procedure. Follow the repair procedure outlined in this Field Service Bulletin (FSB) for
replacement of the existing Twin-Y trailing blades with the newly designed trailing blades and
hardware. See the tables on pages 2 and 3, for required parts.
This bulletin does apply to MACK Trucks Australia.
PV729-FSB722-005_M
USA73318
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
W7104594
Required Parts
Twin-Y Suspension, Trailing Blade, Replacement Parts
Item
Description
Part Number
Qty
1
Trailing Blade
22477420
4
2
Pivot bolt, M22 X220, Huck 360 Bolt
22496392
4
3
Pivot Bolt Collar, M22 X 26.4, Huck 360 Nut
22496430
4
4
Axle Seat Bolts, M18 X 110, Huck 360 Bolt
22356967
16
5
Axle Seat Bolt Collar, M18 X 21.6, Huck 360
Collar
22356966
16
6
Washer M19*34*3
60110294
16
7
Hanger Bracket
21684150
As
Required
8
Hanger Bracket Bolt, 14 87-64
21475330
2#
9
Hanger Bracket Bolt, 14 97-74
21638411
2#
10
Hanger Bracket Bolt 14 107-84
21475333
2#
11
Hanger Bracket Bolt 14 142-119
21710877
2#
Page
2(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
Twin-Y Suspension, Trailing Blade, Replacement Parts (Continued)
Item
Description
Part Number
Qty
12
Hanger Bracket Bolt 20 115-68
22438561
2#
13
Hanger Bracket Bolt Collar 14*21
21475706
8#
14
Hanger Bracket Bolt Collar 20*29
22410765
2#
15
Bendix Cast Brake Cam Tube (Right Side)
85147138
2 ##
16
Bendix Stamped Brake Cam Tube (Right Side)
85147140
2 ##
17
Meritor Cast Brake Cam Tube (Right Side)
85146886
2 ##
18
Meritor Stamped Brake Cam Tube (Right Side)
85146887
2 ##
Note: # These quantities listed in this table are per hanger bracket.
Note: ## One brake cam tube is required per axle (Right Side Only). Determine the number
of axles, which manufacturer, and type of brake cam tube you are going to replace.
Decommissioning the Truck for Repair
You must read and understand the precautions and guidelines in Service Information,
group 70, "General Safety Practices, Frame, Springs, Shocks & Wheels" before performing
this procedure. If you are not properly trained and certified in this procedure, ask your
supervisor for training before you perform it.
NOTE: Information is subject to change without notice. Illustrations are used for reference
only and can differ slightly from the actual vehicle being serviced. However, key
components addressed in this information are represented as accurately as possible.
1 Park the vehicle on a flat and level surface.
2 Apply the parking brake.
3 Place the transmission in neutral or park.
4 Install the wheel chocks.
W7086748
Page
3(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
5 Disconnect the cable from the battery’s negative terminal.
W3086747
Twin-Y Suspension, Trailing Blade, Replacement
Procedure
1 Following safe lifting procedures, lift and support both the frame and axle housings.
2 Remove the wheel nuts.
3 Remove the wheels.
W7104595
Page
4(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
4 Release the park brake.
5 Back off the brakes (slack adjusters).
W7104596
6 Cage the brake chambers.
W7104597
Page
5(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
7 Remove the brake drums.
W7104598
8 Remove the brake linings, brake springs and rollers.
W7104599
Page
6(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
9 Loosen the pivot bolt (1) securing the trailing blade to the frame hanger bracket (left side).
Note: Before loosening the pivot bolt (left side), mark the cam adjustment washers (2) for
re-installation.
W7104600
10 Loosen the pivot bolt and collar securing the trailing blade to the frame hanger bracket
(right Side).
W7104601
Page
7(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
11 Remove the fasteners securing the trailing blade to the top plate and spring seat.
Note: Discard the fasteners. Do not reuse.
W7104602
12 Remove the loosened pivot bolt collars (1), pivot bolts (2) and cam adjustment washers at
frame hanger brackets (left side).
Note: Discard the pivot bolt collars and pivot bolts. Do not reuse.
W7104603
Page
8(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
13 Remove the pivot bolt (1), collar and washers (2) at the frame hanger bracket (right side).
Note: Discard the pivot bolt collars and pivot bolts. Do not reuse.
W7104604
14 With assistance, remove the trailing blades from the axle and frame hanger brackets.
W7104605
Page
9(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
15 Inspect the bushings in the top plate, spring seat and trailing blade for wear or damage
and replace as needed.
W7104606
16 Inspect all frame hanger brackets for wear on the inside mating surface and check for the
trailing blade bushing wear. If significant wear is present, the frame hanger bracket and/or
brackets must be replaced. Failure to do so will result in poor alignment and/or loosening
fasteners.
Note: if needed, refer to 7114-03-02-08 (Trailing Blade, Hanger Bracket, Replacement) for
trailing blade hanger bracket replacement procedures.
W7104607
Page
10(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
17 Remove the cotter pin and the clevis pin securing the brake slack adjuster to brake
chamber clevis.
Note: Discard the old cotter pin. Do not reuse.
Note: Replacement of the brake cam tube is required on the RIGHT SIDE of the truck only.
W7107436
18 Remove the snap ring and shims securing the brake slack adjuster to the brake cam shaft.
Note: Record the orientation of the snap ring and shims for installation purposes.
W7107437
Page
11(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
19 Remove the fastener (1) securing the brake slack adjuster to the bracket (2).
W7107676
20 Rotate the brake slack adjuster until it is clear of the brake chamber clevis as shown in the
figure below.
W7107438
Page
12(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
21 Remove the brake slack adjuster and any spacers from the brake cam shaft.
Note: Record the orientation of the brake slack adjuster and the spacer for installation
purposes.
W7107439
22 Remove the fasteners securing the brake chamber to brake cam tube bracket.
23 Remove the brake chamber from the brake cam tube bracket, position the brake chamber
away from the brake cam tube bracket.
Note: Using a lift or similar platform, support the brake chamber until installation.
W7107440
Page
13(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
24 Remove the fasteners and U-Bolt securing the brake cam tube to the top plate.
W7107677
25 Remove the four fasteners securing the brake cam tube to the brake spider bracket.
W7107441
Page
14(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
26 Pull the S-Cam shaft outward to allow clearance for removal of the brake cam tube.
W7107442
27 Remove the brake cam tube from the brake spider bracket.
W7107443
Page
15(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
28 After removal of the brake cam tube, Inspect the S-Cam shaft for damage to the splines
such as cracks, deformation, and excessive wear. Check the S-Cam shaft head for
cracking or flat spots.
Note: Replace any damaged brake S-Cam shafts before installation of the replacement
brake cam tube.
29 position the replacement brake cam tube over the S-Cam shaft and on the brake spider
bracket.
W7107443
30 Push the S-Cam shaft inward as shown in the figure below.
W7107444
Page
16(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
31 Install the four fasteners securing the brake cam tube to the brake spider bracket.
32 Tighten the fasteners to 60 ± 10 Nm (44 ± 7 ft-lb)
W7107441
33 Install the fasteners and U-Bolt securing the brake cam tube to the top plate.
W7107677
Page
17(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
34 Position the brake chamber on brake cam tube bracket.
35 Install the fasteners securing the brake chamber.
36 Initially tighten the fasteners to 80–100 Nm (59 - 75 ft-lb).
37 Then, tighten the fasteners to 180 – 210 Nm (133 – 155 ft-lb).
W7107440
38 Position the brake slack adjuster and any spacers on the brake cam shaft.
W7107439
Page
18(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
39 Rotate and position the brake slack adjuster in the brake chamber clevis as shown in the
figure below.
W7107438
40 Install the snap ring and shims securing the brake slack adjuster to the brake cam shaft.
W7107437
Page
19(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
41 Install the fastener (1) securing the brake slack adjuster to the bracket (2).
W7107676
42 Install the clevis pin and new cotter pin securing the brake slack adjuster to brake chamber
clevis.
W7107436
Page
20(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
43 Lubricate the brake cam tube at the grease fitting shown in the figure below.
W7107678
44 With assistance, position the replacement trailing blade onto the axle. Install the fasteners
securing the trailing blade.
W7104608
Page
21(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
45 Install the fasteners securing the trailing blade.
Note: Install the M19 Washers (part number 60110294) before installing the trailing arm
bolts.
46 Tighten the fasteners securing the trailing blade to the axle to 440 ± 40 Nm (325 ± 30 ft-lb).
Note: Wait one minute after tightening the fasteners, then tighten them to 440 ± 40 Nm
(325 ± 30 ft-lb) again.
Note: After the nuts (part number 22356966) are finally tightened, DO NOT back the nuts
off of the bolts. If the nuts are backed off of the bolts, remove them, discard and install new
ones. These nuts are for one time use only.
W7104609
Page
22(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
47 Position and loosely attach the opposite end of the trailing blade onto the frame hanger
bracket with the pivot bolts (1), cam adjustment washer (3) (left-hand side), spacer
washers (4) (right-hand side) and pivot bolt collars (2).
Note: Do not tighten the fasteners at the frame bracket until the vehicle is at the correct
ride height.
W7104610
48 Using new brake springs and rollers, Install the brake linings.
W7104599
Page
23(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
49 Install the brake drums.
W7104598
50 Install the wheels.
51 Install the wheel nuts securing the wheels.
52 Tighten the wheel nuts to 645 ± 35 Nm (475 ± 25 ft-lb).
Note: After the truck is lowered and the park brake is set, tighten the wheel nuts again to
specification.
W7104595
Page
24(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
53 Connect the battery cable to the negative (ground) terminal.
W3086758
54 Remove the wheel chocks.
W7086759
Page
25(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
55 Start the engine and fill the air system with air until the proper operating pressure of 120
psi (8 kPa) is obtained. The proper operating will ensure the brakes can be adjusted
properly. Once the proper operating pressure is reached, stop the engine and check for air
leaks.
Note: Ensure the park brake is released before adjusting the brakes.
56 Uncage the brake chambers.
W7104597
57 Adjust the brakes as recommended per slack adjuster manufacturer.
W7104596
Page
26(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
58 Using a floor jack, lift the frame and the axle housing off of the jack stands.
59 Remove the jack stands and remove the jack from under the truck.
60 Check and adjust the ride height. Follow procedure outlined in the Ride Height
Adjustment and Calculations section.
Ride Height Adjustment and Calculations
1 Check all tires for proper inflation. If applicable, adjust tire air pressure to tire
manufacturer’s specifications.
2 Using the dash mounted rear suspension air dump switch, release the air in the rear air
springs or disconnect the leveling rod (1) from the valve lever (2), and use the valve lever
(2) to release pressure from the air springs.
CAUTION
The suspension may drop quickly once pressure is released from the air springs.
W7099902
3 Start the engine and allow the air system to reach the normal operating pressure of 827
kPa (120 psi).
4 Turn off the engine.
5 Inflate the rear air springs with air by using the dash mounted switch or reconnect the
actuator rod to the load leveling valve lever.
Note: Ensure the air system is at a normal operating pressure of 827 kPa (120 psi).
6 Free and center all suspension joints by slowly moving the vehicle back and forth twice
without using the brake.
Note: When coming to a complete stop, ensure the brakes (parking and service) are
released.
Page
27(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
7 Chock the front wheels.
W7086748
8 Using a tape measure, measure and record the height of the frame rail.
Note: The ride height measurement is dependent on frame size.
9 Measure and record the distance from the floor to the center of the axle
(Measurement – A).
10 Measure and record the distance from the bottom edge of the frame rail to the floor
(Measurement – B).
11 Subtract measurement – A from measurement – B to calculate the ride height
(A – B = ride height).
Note: Use the table below to determine if the truck is at the proper ride height.
Ride Height (Unloaded)
Frame Height
Frame Type
Ride Height
266 mm (10.4 in)
RRH-200
210 ± 5 mm (8.27 ± 0.2 in)
300 mm (11.8 in)
RRH–180
193 ± 5 mm (7.6 ± 0.2 in)
Page
28(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
12 Adjust the ride Height if needed. Slightly Loosen the fastener (1) securing the leveling
valve to the frame rail.
13 Using the ride height adjustment tool (3) (part number J-44544), adjust the load leveling
valve (2) until the ride height is within specification.
Note: The suspension ride height is adjusted by turning the load leveling valve
CLOCKWISE (to raise) or COUNTERCLOCKWISE (to lower) the ride height.
W7104611
14 Tighten the fastener (1) securing the load leveling valve (2) to the frame to 175 ± 40 Nm
(129± 30 lb-ft).
W7104656
Page
29(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
15 Repeat steps 8 – 14 to validate the ride height and confirm the accuracy of the leveling
valve adjustment.
16 Using the dash mounted rear suspension air dump switch, release the air in the rear air
springs or disconnect the leveling rod (1) from the valve lever (2), and use the valve lever
(2) to release pressure from the air springs.
CAUTION
The suspension may drop quickly once pressure is released from the air springs.
W7099902
17 If applicable, connect the suspension leveling rod (1) to the valve control lever (2).
W7099902
Page
30(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
18 Start the engine, build air pressure to the proper operating pressure, and stop engine.
19 Fill the rear air springs.
Note: Ensure the air pressure is at the proper operating pressure.
20 Using a tape measure, re-check the ride height.
Note: If the ride height is not within specifications, check the leveling valve and other
suspension components for excessive wear or damage.
21 Apply the parking brake.
22 Using the previous cam alignment washer markings, Align the cam alignment washers (left
side only).
Note: This should assist in getting close to the proper alignment.
23 With the truck at correct ride height, tighten fasteners at the frame hanger bracket to 750 ±
75 Nm (550 ± 55 ft-lb).
W7104645
Page
31(32)
Mack Trucks, Inc.
Field Service Bulletin
Date
10.2015
Group
No.
Release
722
005
01
24 Remove the wheel chocks.
W7086759
25 Perform an alignment on the drive axles.
Reimbursement
This repair may be eligible for reimbursement
if a product failure was experienced within
time and mileage limits of the applicable
Warranty coverage. Reimbursement is
obtained via the normal claim handling
process.
UCHP
Reimbursement
eWarranty
Reimbursement
Claim Type (used only when uploading from
the Dealer Bus. Sys.)
01
01
Primary Labor Code (Twin-Y Suspension, Trailing
Blade, Replacement) Mack Axles
7229-03-09-02
9.1 hrs
1353F–01–80
9.1 hrs
Causal Part
21649231
21649231
Labor Code
MACK Trucks North America reserves the right to make any changes in design or to make
additions to or upon its products without incurring any obligations to install the same on
vehicles previously built.
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