FSB 722-005
Service Bulletin Details
Public Details for: FSB 722-005
Twin y suspension, trailing blade, replacement. 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
Models from 2016
2016 MACK CHU |
2016 MACK CXU |
Models from 2015
2015 MACK CHU |
2015 MACK CXU |
Models from 2014
2014 MACK CHU |
2014 MACK CXU |
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. Page 32(32)