SERVICE BULLETIN (Also applies to Mack Trucks Australia) NUMBER: SB-423-002 DATE: 8/23/02 MODEL: All with FF981 Front Axle ARVINMERITOR UNITIZED FRONT WHEEL HUB INSPECTION AND MAINTENANCE The ArvinMeritor front steer axle model FF981 is equipped with unitized wheel hubs. These wheel hubs, which are identified by the two half moons embossed in the center of the hubcap, are sealed and greased for life, and do not require lubrication at any regular service intervals. 1 Figure 1 ArvinMeritor Unitized Wheel Hub Identification To ensure long life and optimum performance from these wheel hubs, however, inspections must be performed at the following intervals: Detailed Inspection After the initial 200,000 miles (321 800 km) of service. After every 200,000 miles (321 800 km) of service. Basic Inspection After the initial 250,000 miles (402 250 km) of service, and thereafter, at each 50,000 mile (80 467) interval, or At the fleet's most frequent preventive maintenance inspection interval. SB-423-002 Page 1 of 9 SERVICE PUBLICATIONS, ALLENTOWN, PA 18105 MACK TRUCKS, INC. 2002
The following table summarizes the unitized wheel hub inspection intervals. Mileage (Kilometer) Interval Basic Inspection Detailed Inspection 200,000 miles (321 800 km) X 250,000 miles (402 250 km) or at most frequent preventive maintenance interval X 300,000 miles (482 700 km) or at most frequent preventive maintenance interval X 350,000 miles (563 150 km) or at most frequent preventive maintenance interval X 400,000 miles (643 600 km) X If the vehicle is equipped with anti-lock brakes on the steer axle and driver reports have indicated that the ABS lamp has been turning on, a basic inspection must be performed to determine possible looseness of the wheel hub. Excessive wheel end play can cause the ABS sensor gap to be out of adjustment. PROCEDURES Unitized wheel hubs are sealed and greased for life. Disassembling, repairing or lubricating a unitized wheel hub will void the ArvinMeritor warranty. The detailed and basic inspections outlined in this bulletin are performed without disassembling the wheel hub. Basic Inspection 1. Park the vehicle on a level surface, apply the parking brake and block the wheels to prevent the vehicle from moving. 2. Raise the vehicle so that the front wheels are off the ground and support the chassis on jack stands of adequate capacity to support the weight of the vehicle. Support the vehicle on jack stands of adequate capacity. Do not work on or around a vehicle that is supported only by a hydraulic jack, as a hydraulic jack can fail suddenly and unexpectedly, resulting in severe personal injury or death. 3. Visually inspect the unitized wheel hub as the wheel hub and tire assembly are being rotated. Verify that the assembly rotates smoothly and without any noise. SB-423-002 Page 2 of 9
If the wheel hub assembly does not rotate smoothly, or if noise is heard while rotating, a detailed inspection must be performed. Refer to the instructions outlined under the heading Detailed Inspections. 4. Grasp the wheel hub/tire assembly at the nine and three o'clock positions. Check for vertical and horizontal movement by applying approximately 50 lbs (23 kg) of force by hand. Looseness or movement should not be felt. If looseness or movement is felt, perform a detailed inspection to determine the cause, such as a worn kingpin or bushings, wheel-to-hub mounting end play, unitized wheel hub end play or a combination of all three. To determine wheel hub end play, refer to the procedures outlined under the heading Detailed Inspections. To aid in determining the cause of looseness or movement, first check the wheel-to-hub mounting. Verify that the wheel is mounted correctly and that the lug nuts are properly torqued (refer to the Maintenance and Lubrication Manual, TS494, for procedures on torquing wheel lug nuts). After checking wheel-tohub mounting, apply the service brakes to lock the wheel hub and spindle assembly together, then again, check for looseness or movement. If movement is noticed, the kingpin or kingpin bushings are probably worn. If applying the service brake eliminates the movement, proceed to the instructions outlined under the heading Detailed Inspection to determine the wheel hub end play. Detailed Inspection 1. Park the vehicle on a level surface, apply the parking brake and block the wheels to prevent the vehicle from moving. 2. Remove the hubcap. 3. Raise the vehicle so that the front wheels are off the ground and support the chassis on jack stands of adequate capacity to support the weight of the vehicle. Support the vehicle on jack stands of adequate capacity. Do not work on or around a vehicle that is supported only by a hydraulic jack, as a hydraulic jack can fail suddenly and unexpectedly, resulting in severe personal injury or death. SB-423-002 Page 3 of 9
The inboard and outboard hub seals may purge a small amount of grease that is visible during the following procedures. This is a normal occurrence. 4. Remove the wheel rim/tire assembly, then remove the brake drum. 5. Attach the magnetic base of a dial indicator to the end of the spindle, and position the indicator stylus perpendicular against the mounting face of the wheel hub. 2 3 Figure 2 Dial Indicator Installed on Wheel Hub 6. Zero the dial indicator. Without rotating the wheel hub, grasp the hub at the nine and three o'clock positions. Push the wheel hub straight IN, then pull it straight OUT. Note the reading indicated on the dial indicator. If the measurement on the dial indicator is less than 0.003 (0.08 mm), proceed to step 9. If the measurement on the dial indicator is 0.003 (0.08 mm) or greater, remove the OUTER bearing nut and tabbed washer. Using an accurately calibrated torque wrench, tighten the INNER wheel bearing nut between 500 700 lb-ft (679 949 N m) while rotating the hub a minimum of five rotations. Figure 3 Unitized Wheel Hub Assembly SB-423-002 Page 4 of 9
7. Install the tabbed washer and OUTER wheel bearing nut. Tighten the OUTER nut between 200 300 lb-ft (271 476 N m). The inner and outer wheel bearing nuts are identical, but the torque values are different. 8. Remeasure wheel hub end play by grasping the hub at the nine and three o'clock positions, then, without rotating the hub, push the hub straight IN and pull straight OUT. Note the measurement indicated on the dial indicator. If the measurement on the dial indicator is greater than 0.003 (0.08 mm) but less than 0.006 (0.15 mm), record the measurement in the maintenance log and perform a basic inspection at the next regularly scheduled interval, or after 50,000 miles (80 467 km), whichever occurs first. If the measurement on the dial indicator is 0.006 (0.015 mm) or greater, replace the unitized wheel hub. 9. Verify that the wheel hub rotates smoothly and that no noise can be heard during rotation. If noise is heard or the hub does not rotate smoothly, replace the wheel hub. 10. Bend the tabs of the locking washer over the flats of the outer wheel bearing nut and also the inner wheel bearing nuts. Bend a minimum of one tab to each nut. Unitized Wheel Hub Installation If replacement of the unitized wheel hub assembly is necessary, installation instructions are as follows: The spindle O-ring (part No. 8235-5X1301) prevents contaminants from entering the assembly. When a unitized wheel hub is removed, install a new O-ring when installing the hub assembly. If a cracked unitized wheel hub is suspected, use only dye penetrant inspection techniques. Use care not to allow penetrant fluids to enter the bore of the hub unit. Do not use fluid immersion-based crack inspection techniques, as these fluids can enter the joint between the inner bearing cones through the bore of the hub unit and damage the lubricant. Serious personal injury and damage to components can result. SB-423-002 Page 5 of 9
1. Using a clean, lint-free shop cloth, clean the wheel hub inner bore and spindle. Do not apply any solvents. 2. Check the hub bore for any obstructions, and check the spindle for any nicks or burrs. 3. Coat the inside of the unitized wheel hub with an anti-seize or anti-fretting compound such as Dow Corning Molykote D. Make certain to cover the inner and outer bearing races. Do not apply anti-seize or anti-fretting compounds to the spindle threads. Remove any anti-seize or anti-fretting compounds that may have dripped onto the spindle threads. Do not apply anti-seize or anti-fretting compounds to the spindle threads, as these compounds decrease the capability of a fastener to maintain sufficient clamp load. Without sufficient clamp load, the wheels may come loose and separate from the vehicle, resulting in serious personal injury and damage to components. 4. Coat a new O-ring (part No. 8235-5X1301) with an anti-seize or anti-fretting compound such as Dow Corning Molykote D, then slide the O-ring onto the spindle. The O-ring must be positioned against the knuckle journal. Align the unitized wheel hub STRAIGHT onto the spindle. Do not allow the assembly to misalign and contact the spindle threads. Bearing damage can occur that requires replacement of the entire unitized wheel hub assembly. 5. Carefully align the unitized wheel hub bore with the spindle and slide the hub STRAIGHT onto the spindle. If the unitized wheel hub does not slide on easily, do not force it onto the spindle. The hub can become jammed on the spindle if it is not aligned correctly with the spindle. If the unitized wheel hub becomes jammed on the spindle, remove the hub from the spindle carefully so that the inner bearings do not disassemble or loosen from the hub. 6. Install the INNER D washer and the INNER wheel bearing nut. Tighten the INNER bearing nut between 500 700 lb-ft (679 949 N m) while rotating the hub assembly a minimum of five rotations. SB-423-002 Page 6 of 9
4 Figure 4 Unitized Wheel Hub Assembly 7. Install the tabbed locking washer and the OUTER wheel bearing nut. Tighten the OUTER wheel bearing nut between 200 300 lb-ft (271 476 N m). The inner and outer wheel bearing nuts are identical, but the torque values are different. 8. Bend the tabs of the locking washer over the flats of the outer wheel bearing nut and also the inner wheel bearing nuts. Bend a minimum of one tab to each nut. Hubcap Installation In most instances, hubcaps can be reused. If, however, any of the following conditions are observed while tightening the hubcap, it should be replaced with a new hubcap: The hubcap jumps threads and makes a popping sound while being tightened. The hubcap begins to yield because the threads are stripped. Correct torque specifications cannot be achieved. Plastic and aluminum hubcaps are interchangeable. SB-423-002 Page 7 of 9
Plastic Hubcap It is not necessary to remove residual Loctite sealant from the original hubcap installation. 1. Wipe the inner threads of the wheel hub with a clean, lint-free shop cloth. Do not use compressed air, solvent or power washers to clean the hubcap threads inside the wheel hub. Use a wire brush to remove grease or mud from the hubcap threads inside the wheel hub, then wipe the threads with a clean, lint-free shop cloth. Use only ArvinMeritor RTV sealant (part No. 2297-Z-7098), Three Bond, or Loctite Ultra Grey Adhesive Sealant number 18581 when servicing a unitized wheel hub assembly. Do not use any other brand of silicone sealant, as other brands may cause corrosion, damage and incompatibility between the wheel hub components. Serious personal injury and damage to components can result. 2. Apply a continuous 1/8 3/16 (3 5 mm) bead of RTV sealant to the outside first thread, around the entire circumference of the hubcap. (Refer to the WARNING above for silicone sealants that can be used.) 5 Figure 5 Applying Silicone Sealant 3. Install the plastic hubcap and tighten by hand. 4. Using the proper size socket and an accurately calibrated torque wrench, tighten the plastic hubcap between 50 100 lb-ft (67 135 N m). Disregard the torque value that is embossed on the hubcap. SB-423-002 Page 8 of 9
Aluminum Hubcaps 1. Use a wire brush to clean the hubcap threads inside the wheel hub, and also the external threads of the hubcap. 2. Apply Loctite No. 17430 anaerobic gasket sealant to the hubcap threads. 3. Install the hubcap and tighten by hand until seated. 4. Using the correct size socket and an accurately calibrated torque wrench, tighten the hubcap between 325 375 lb-ft (440 508 N m). SB-423-002 Page 9 of 9