chap95 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 95, the reader should be able to: • • • Prepare for the ASE Manual Drive Train and Axles (A3) certification test content area “B” (Transmission Diagnosis and Repair) and content area “C” (Transaxle Diagnosis and Repair) Explain how to calculate gear ratios Name the parts of a typical manually shifted transmission/transaxle 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 95, the reader should be able to: • • • Describe how the synchronizer assembly allows for smooth, clash-free shifting Describe the different types of lubricants that may be used in a manual transmission/transaxle Diagnose a difficult-to-shift manual transmission/transaxle 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: axis back taper • bell housing • bevel gear • blocker ring cluster gears • cluster shaft • cluster gear • constant-mesh gear • counter gears • countershaft direct drive • drive gear • driven gear extension housing • external gears fifth gear • final drive assembly • first gear • fourth gear • front bearing retainers 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 KEY TERMS: gear reduction helical gear • hypoid gear set input shaft • internal ring gears keys lay shaft main drive pinion assembly • main gear • main shaft neutral 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 KEY TERMS: output shaft • overdrive pinion gear quill reverse second gear • sliding reverse gear • sliding sleeve • springs • spur gear • stop ring • synchronizer assemblies • synchronizer ring third gear • transmission case 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 NEED FOR A TRANSMISSION A vehicle requires a lot of torque to start off and to climb hills, yet it does not require as much torque to move on level ground Torque is a twisting or turning force that is exerted on the input shaft of a transmission/transaxle An engine produces increasing torque as its speed increases up to a certain point where the torque output starts to decrease To get a vehicle moving or to accelerate up a hill, it is desirable to use a transmission that allows the engine speed to be increased even though the vehicle speed may be low Using gears allows the engine speed to increase at low vehicle speeds yet still permits it to drop at higher speeds to save fuel and reduce emissions 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 First gear: Vehicle speed is low, engine speed is high Second gear: Vehicle speed increases, engine speed decrease Third gear: Vehicle speed continues to increase, engine speed is kept in a narrow range Fourth gear: Again, the vehicle speed is increasing, yet engine speed is about the same as in third gear What Is the Difference Between a Transmission and a Transaxle? A transmission is used on rear-wheel-drive vehicles, whereas a transaxle is usually used on front-wheel-drive vehicles A vehicle equipped with a transmission uses a separate differential to split the torque equally to the drive wheels.A transaxle includes a differential assembly In a transaxle, the differential, sometimes called the final drive unit, is incorporated in the construction of the transmission 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 GEAR TYPES The simplest type of gear is the spur gear, consisting of a gear blank with straight-cut teeth around its entire circumference All gear teeth lie parallel to the centerline, or axis, of the gear The teeth are shaped so they can mesh without slippage with a second spur gear’s teeth positioned along a parallel axis Figure 95–1 Spur gears have straight-cut teeth 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 A helical gear, although similar to a spur gear, has its teeth cut at an angle to the axis of the gear This enables more teeth, 2.5 to 3.5, to mesh at a time than the spur gear The angle allows the teeth to mesh gradually, rather than all at once As a result, helical gears run quieter than spur gears Helical gears have two disadvantages Each gear pushes against its shaft parallel to its axis Special bearings are needed to protect the gearbox from this type of axial, or thrust, loading Because of the increased contact area, helical gears create more friction than spur gears See Figures 95–2 and 95–3 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 CAUTION: Perfectly round cylinders can be distorted whenever another part of the engine is bolted and torqued to the engine block For example, it has been determined that after the cylinders are machined, the rear cylinder bore can be distorted as much as 0.006 inch (0.15 millimeter) out-of-round after the bell housing is bolted onto the block! To help prevent this distortion, always apply the specified torque to all fasteners going into the engine block and tighten in the recommended sequence The clutch release yoke should be checked for free movement Usually, the clutch release bearing is replaced, ensuring that the new bearing is securely attached to the clutch release yoke The transmission can then be installed The clutch shaft must be guided straight into the clutch disk and pilot bearing The clutch shaft is rotated, as required, to engage in the splines of the clutch disk The assembly bolts are secured when the transmission fully mates with the bell housing 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 Complete the installation by attaching the transmission/ transaxle mount, driveshaft (drive axle shafts), vehicle speed sensor, and reverse (backup) light switch CAUTION: Always adjust the clutch free play before starting the engine to help prevent thrust bearing damage 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 GEAR LUBRICATION After installation of the transmission/transaxle, the unit should be filled with the correct lubricant The various lubricants, their general use, and their American Petroleum Institute (API) rating: GL-1 Straight mineral oil GL-2 Worm-type gear lubricant GL-3 Mild-type EP lubricant (will not protect hypoid gears) GL-4 ‑EP-type lubricant (OK for manual transmissions/transaxles) GL-5 EP-type ok for hypoid gears and for Mil-L2150B (military) CAUTION: Failure to use the specified manual transmission/transaxle lubricant could cause hard shifting and possible transmission damage 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 Manual transmissions/transaxles require one of the following: SAE 80W-90 (GL-4) gear lube STF (synchromesh transmission fluid), but with friction characteristics designed for manual transmissions (see Figure 95–43) ATF (automatic transmission fluid) Engine oil (usually SAE 5W-30) Figure 95–43 Some manual transmissions/transaxles require synchromesh transmission fluid 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 Headless Bolt Trick Sometimes parts not seem to line up correctly Try this tip the next time Cut the head off extra-long bolts that are of the same diameter and thread as those being used to retain the part, such as a transmission Use a hacksaw to cut a slot in the end of these guide bolts for a screwdriver slot.Install the guide bolts; then install the transmission Use a straightblade screwdriver to remove the guide bolts after securing the transmission with the retaining bolts Figure 95–44 Headless, long bolts can be used to help install a transmission to the engine 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 NV-1500 Manual Transmission Svc 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 NV-1500 Transmission Svc (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 NV-1500 Transmission Svc (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 NV-1500 Transmission Svc (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 NV-1500 Transmission Svc (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 NV-1500 Transmission Svc 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 transmission is required both to provide the torque necessary to the drive wheels to get the vehicle moving from a stop and to provide economical cruising on the highway A gear ratio is determined by dividing the number of teeth on the driven gear (output) by the number of teeth on the driving gear (input) A ratio is always expressed as a number relative to one rotation of the output gear An overdrive ratio is a ratio that results in the output gear rotating faster than the input gear; the first number of this ratio is less than one A spur gear is a gear with straight teeth, and a helical-cut gear is a gear with angled teeth 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.) The input shaft is splined to the clutch disc The output shaft is also called the main shaft A countershaft is another shaft inside a transmission/transaxle which provides another set of gears to produce the necessary gear ratios Care should be taken to not damage the parts of the transmission/ transaxle during disassembly Always consult the factory service manual for the exact procedures to follow, especially regarding using a hydraulic press to press gears off or on the shafts A synchronizer assembly permits a shift to be made without gear clash 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.) The parts of a typical synchronizer include the synchronizer sleeve, hub, and ring 10 A transaxle includes a final drive unit that splits the torque to the two front drive wheels and allows the drive wheels to rotate at different speeds while traveling around a corner or over bumpy roads 11 A manual transmission/transaxle may use one of four possible lubricants including gear lube, synchromesh transmission fluid (STF), automatic transmission fluid (ATF), or engine oil 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 ... noisy during operation Helical-cut gears, on the other hand, operate quietly but create a force in line with the axis of the gears due to the angle of the gear teeth Automotive Technology: Principles,... relation to each other is the gear ratio Gear ratio is expressed as the number of rotations the drive gear must make in order to rotate the driven gear through one revolution To obtain a gear ratio,... combination provides an overdrive ratio of 0.33:1 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc