start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 86, the reader should be able to: • • • Prepare for ASE Suspension and Steering (A4) certification test content area “B” (Suspension System Diagnosis and Repair) Explain how to perform a road test, a dry park test, a visual inspection, and a bounce test Discuss the procedures for testing load-carrying and follower-type ball joints Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 86, the reader should be able to: • • • Describe ball joint replacement procedures List the steps required to replace control arm and stabilizer bar bushings Explain routine service procedures of the suspension system Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: a-arm cow catcher • cuppy tire wear dry park test • durometer indicator ball joints kingpin • pinch bolt • radius rod SLA • steering knuckle • strut suspension twin I-beam Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 FRONT SUSPENSION TYPES Solid Axles Early cars and trucks used a solid (or straight) front axle to support the front wheels A solid-axle front suspension is very strong and is still being used in the manufacture of medium and heavy trucks The main disadvantage of solid-axle design is its lack of ride quality When one wheel hits a bump or dip in the road, the forces are transferred through the axle to the opposite wheel Solid axles are currently used in the rear of most vehicles See Figure 86–1 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 86–1 Most early vehicles used single straight axles Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Kingpins To allow the front wheels to rotate for steering the end of many solid I-beam or tube axles have kingpins These are hardened steel pins that attach the steering knuckle to the front axle, allowing the front wheels to move for steering Kingpins usually have grease fittings to lubricate the kingpin bushings Failure to keep these bushings lubricated with chassis grease can cause wear and freeplay or can cause the pins to become galled (seized or frozen), resulting in hard steering and/or loud noise while turning See Figure 86–2 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 86–2 Typical kingpin used with a solid axle Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Twin I-Beams A twin I-beam front suspension was used for over 30 years on Ford pickup trucks and vans Strong steel twin beams that cross provide independent front suspension operation with the strength of a solid front axle Early versions used kingpins; later models used ball joints to support the steering knuckle and spindle Coil springs are usually used on twin I-beam suspensions, even though the original design and patent used leaf springs A radius rod is attached to each beam and is anchored to the frame of the truck using rubber bushings, which allow the front axle to move up and down while still insulating road noise and vibration from the frame and body See Figure 86–3 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 86–3 Twin I-beam front suspension Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 TORSION BARS Adjustment Most torsion bar suspensions are designed with an adjustable bolt to permit the tension on the torsion bar to be increased or decreased to change the ride height Unequal side-to-side ride height can be corrected by adjusting (turning) the torsion bar tension bolt See Figure 86–52 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Torsion bar adjustment should be made if the difference in ride height from one side to another exceeds 1/8 in.(0.125 in or 3.2 mm) If the ride height difference side to side is greater than 1/8 in., the vehicle wander or be unstable, with constant steering wheel movements required to maintain straight-ahead direction Figure 86–52 By rotating the adjusting bolt, the vehicle can be raised or lowered.seated Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 CONTROL ARM BUSHINGS Diagnosis Defective control arm bushings are a common source of vehicle handling and suspension noise problems Most suspension control arm bushings are constructed of three parts: an inner metal sleeve, the rubber bushing itself, and an outer steel sleeve (Some vehicles use a two-piece bushing that does not use an outer sleeve.) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Replacement To remove an old bushing from a control arm, the control arm must first be separated from the suspension and/or frame of the vehicle Several methods can be used to remove the bushing from the control arm, but all methods apply force to the outer sleeve While an air chisel is frequently used to force the steel sleeve out of the suspension member, a puller tool is most often recommended by General Motors See Figure 86–53 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 The puller can be used to remove the old bushing and install the replacement bushing without harming the control arm or the new bushing Figure 86–53 An adapter and a press or large clamp are used to remove the old bushing from the control arm and to install a new bushing All bushings should be tightened with the vehicle on the ground and the wheels in a straight-ahead position; this prevents the rubber bushing from exerting a pulling force on the suspension Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 NOTE: Some replacement control arm bushings have a higher durometer, or hardness, rating than the original Urethane bushings are often used in sporty or race-type vehicles and deflect less than standard replacement bushings These harder bushings also transfer more road noise, vibration, and harshness to the body The upper control arm bushings can be replaced in most vehicles that use a short/long-arm-type suspension by following just four easy steps: Step #1 Raise the vehicle and support the lower control arm with a safety stand or floor jack Step #2 Disconnect the upper control arm from the frame by removing the frame-attaching nuts or bolts Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Step #3 Using the upper ball joint as a pivot, rotate the upper control arm outward into the wheel well area With the control arm accessible, it is much easier to remove and replace the upper control arm pivot shaft and rubber bushings Step #4 After replacing the bushings, simply rotate the upper control arm back into location and reattach the upper control arm pivot shaft to the vehicle frame NOTE: An alignment should always be performed after making any suspension-related repairs Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 PHOTO SEQUENCE Strut Replacement Step-By-Step Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 PHOTO SEQUENCE Strut Replacement (cont.) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 PHOTO SEQUENCE Strut Replacement (cont.) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 PHOTO SEQUENCE Strut Replacement Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman (cont.) ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY A thorough road test of a suspension problem should include driving beside parked vehicles and into driveways in an attempt to determine when and where the noise occurs A dry park test should be performed to help isolate defective or worn suspension components Ball joints must be unloaded before testing The ball joints used on vehicles with a MacPherson strut suspension are not load carrying Wear-indicator ball joints are observed with the wheels on the ground Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) Always use a taper-breaker puller or two hammers to loosen tapered parts to remove them Never use heat unless you are replacing the part; heat from a torch can damage rubber and plastic parts When installing a tapered part, always tighten the attaching nut to specifications Never loosen the nut to install a cotter key If the cotter key will not line up with a hole in the tapered part, tighten the nut more until the cotter key hole lines up with the nut and stud Defective shock absorbers can cause ride harshness as well as frequent bottoming out on rough roads Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) Always follow manufacturers’ recommended procedures whenever replacing springs or MacPherson struts Never remove the strut end nut until the coil spring is compressed and the spring force is removed from the upper bearing assembly Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 end Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458