chap96 pps Automotive technology at University of Cambridge

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 96, the reader should be able to: • • • Prepare for ASE Suspension and Steering (A4) certification test content area “C” (Related Suspension and Steering Service) Name driveshaft and U-joint parts, and describe their function and operation Describe how CV joints work 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 96, the reader should be able to: • • Explain how the working angles of the Ujoints are determined List the various types of CV joints and their applications 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: cardan joints • center support bearing • CV joint boot • CV joints double-cardan joints • drive axle shaft • driveshaft fixed joint half shaft plunge joint • propeller shaft Rzeppa joint • spider trunnions • universal joints 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 A drive axle shaft transmits engine torque from the transmission or transaxle (if front wheel drive) to the rear axle assembly or drive wheels Driveshaft is the term used by the Society of Automotive Engineers (SAE) to describe the shaft between the transmission and the rear axle assembly on a rear-wheel-drive vehicle The SAE term will be used throughout this textbook 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 A drive axle shaft transmits engine torque from the transmission or  transaxle (front wheel drive) to the rear axle assembly or drive wheels.  Figure 96–1 Typical rear-wheel-drive power train arrangement The engine is mounted longitudinal (lengthwise) 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 96–2 Typical front-wheel-drive power train arrangement The engine is usually mounted transversely (sideways) 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 96–3 Typical driveshaft (also called a propeller shaft) The drivershaft transfers engine power from the transmission to the differential A typical driveshaft is a hollow steel tube.  A splined end yoke is welded onto one end  that slips over the splines of the output shaft  of the transmission. An end yoke is welded  onto the other end of the driveshaft. Some  driveshafts use a center support bearing 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 DRIVESHAFT DESIGN Most driveshafts are constructed of hollow steel tubing. The forces  are transmitted through the surface of the driveshaft tubing. The  surface is in tension, and cracks can develop on the outside surface  of the driveshaft due to metal fatigue. Driveshaft tubing can bend  and, if dented, can collapse.  Figure 96–4 This driveshaft failed because it had a slight dent caused by a rock When engine torque was applied, the driveshaft collapsed, twisted, and then broke 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 Most rear­wheel­drive cars and light trucks use a one­ or two­piece driveshaft. A steel tube driveshaft has a  maximum length of about 65 in. (165 cm). Beyond this length, a center support bearing, called a steady bearing or hanger  bearing, must be used Some vehicle manufacturers use aluminum driveshafts; these can be as long as 90 in. (230 cm) with no  problem. Many extended­cab pickup trucks and certain vans use aluminum driveshafts to eliminate the need  (and expense) of a center support bearing Composite­material driveshafts are also used in some vehicles. These carbon­fiber­plastic driveshafts are very  strong yet lightweight, and canbe made in extended lengths without the need for a center support bearing See Figure 96–5 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 Drive Axle Shafts  Unequal­length drive axle shafts (also called half shafts) result in unequal  drive axle shaft angles to the front drive wheels. This unequal angle often results in a pull on the  steering wheel during acceleration This pulling to one side during acceleration due to unequal engine torque being applied to the  front drive wheels is called torque steer To help reduce the effect of torque steer, some vehicles are manufactured with an intermediate  shaft that results in equal drive axle shaft angles. Both designs use fixed outer CV joints with  plunge­type inner joints See Figure 96–17 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 96–17 Unequal-length driveshafts result in unequal drive axle shaft ngles to the front drive wheels This unequal angle side-to-side often results in a steering of the vehicle during acceleration called torque steer By using an intermediate shaft, both drive axles are the same angle and the torque steer effect is reduced (Courtesy of Dana Corporation) See the entire illustration on Page 1244 of your textbook.  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 96–17 Unequal-length driveshafts result in unequal drive axle shaft ngles to the front drive wheels This unequal angle side-to-side often results in a steering of the vehicle during acceleration called torque steer By using an intermediate shaft, both drive axles are the same angle and the torque steer effect is reduced (Courtesy of Dana Corporation) See the entire illustration on Page 1244 of your textbook.  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 What Is That Weight for on the Drive Axle Shaft? Some drive axle shafts are equipped with what looks like a balance weight It is actually a dampener weight used to dampen out certain drive line vibrations The weight is not used on all vehicles and may or may not appear on the same vehicle depending on engine, transmission, and other options The service technician should always try to replace a defective or worn drive axle shaft with the exact replacement When replacing an entire drive axle shaft, the tech should always follow the manufacturer instructions regarding transferring the weight to the new shaft Figure 96–18 A typical drive axle shaft with dampener weight 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 Inner CV joints designed to move axially, or plunge: Tripod. See Figure 96–19 Cross groove. See Figure 96–20 Double offset. See Figure 96–21 Figure 96–19 A tripod joint is also called a tripot, tripode, or tulip design (Courtesy of Dana Corp) 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 96–20 A cross-groove plunge joint is used on many German front-wheel-drive vehicles and as both inner and outer joints on the rear of vehicles that use an independent-type rear suspension (Courtesy of Dana Corporation) 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 96–21 Double-offset ball-type plunge joint (Courtesy of Dana Corporation) 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 CV Joint Boot Materials  The pliable boot surrounding the CV  joint, or CV joint boot, must be able to remain flexible under all  weather conditions and still be strong enough to avoid being  punctured by road debris.  NOTE: Some aftermarket companies offer a split­style replacement CV  joint boot. Being split means that the boot can be replaced without having  to remove the drive axle shaft. Vehicle manufacturers usually do not  recommend this type of replacement boot because the joint cannot be  disassembled and properly cleaned with the drive axle still in the vehicle.  The split boots must also be kept perfectly clean (a hard job to do with all  the grease in the joint) in order to properly seal the seam on the split boot 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 Four basic types of boot materials used over CV joints: Natural rubber (black) uses a bridge­type stainless steel clamp Silicone rubber (gray) is a high­temperature­resistant material  that is usually only used in places that need heat protection,  such as the inner CV joint of a front­wheel­drive vehicle Hard thermoplastic (black) A hard plastic material requiring  heavy­duty clamps and much torque (about 100 lb­ft!) Urethane (usually blue) is a type of boot material usually  found in an aftermarket part. For examples of various types of CV joint boots depending on the manufacturer of the CV  joints and shafts See Figure 96–22 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 96–22 Getting the correct book kit or parts from the parts store is more difficult on many Chrysler front-wheel-drive vehicles because Chrysler has used four different manufacturers for its axle shaft assemblies (Courtesy of Dana Corporation) It is important that boot seals be inspected regularly and replaced if  damaged. Seal retainers are used to provide a leakproof connection  between the boot seal and the housing or axle shaft 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 CV Joint Grease  CV joints require special greases. Most CV  joint grease is molybdenum­disulfide­type grease, commonly  referred to as moly grease. The exact composition of grease can  vary depending on the CV joint manufacturer.  The grease supplied with a replacement CV joint or boot kit should be the only grease used The exact mix of chemicals, viscosity, wear, and corrosion­resistant  properties varies from one CV joint application to another.  Some techs mistakenly think the color of the grease determines in  where it is used. The color—such as black, blue, red, or tan—is  used to identify the grease during manufacturing and packaging  as well as to give the grease a consistent, even color (due to  blending of various ingredients in the grease) 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 exact grease to use depends on many factors, including: The type (style) of CV joint. For example, outer (fixed) and  inner (plunging) joints have different lubricating needs The location of the joint on the vehicle. For example, inner  CV joints are usually exposed to the greatest amount of heat The type of boot. The grease has to be compatible with the  boot material 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 The driveshaft of a rear­wheel­drive vehicle transmits engine  torque from the transmission to the differential Driveshaft length is usually limited to about 65 inches due to  balancing considerations unless a two­piece or a composite  material shaft is used Universal joints (U­joints) allow the driveshaft to transmit  engine torque while the suspension and the rear axle assembly  are moving up and down during normal driving conditions Acceptable working angles for a Cardan­type U­joint fall  within 1/2 to 3 degrees. Some angle is necessary to cause the  roller bearings to rotate; a working angle of greater than 3  degrees can lead to driveline vibrations 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.) Constant velocity (CV) joints are used on all front­wheel­ drive vehicles and many four­wheel­drive vehicles to provide  a smooth transmission of torque to the drive wheels regardless  of angularity of the wheel or joint Outer or fixed CV joints commonly use a Rzeppa design,  while inner CV joints are the plunging or tripod type 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 ... the driveshaft. If the angles? ?of? ?both joints are nearly equal, the  acceleration and deceleration? ?of? ?one joint is offset by the alternate  deceleration and acceleration? ?of? ?the second joint.  It is very important that both U­joints operate? ?at? ?about the same angle to prevent excessive driveline vibration. ... The location? ?of? ?the joint on the vehicle. For example, inner  CV joints are usually exposed to the greatest amount? ?of? ?heat The type? ?of? ?boot. The grease has to be compatible with the  boot material Automotive Technology: Principles, Diagnosis, and Service,... This produces pulsations and a noticeable vibration or surge The higher the shaft speed and the greater the angle? ?of? ?the joint, the greater the pulsations Continued Automotive Technology: Principles, Diagnosis,