Chapter 5
Transmission Designs/Rebuilding Transmissions
Upon completion and review of this chapter, the student should be able to:
Classroom Manual Objectives· Explain the differences between a transaxle and a transmission.
· Describe the total driveline for FWD, RWD, and 4WD vehicles.
· Explain how to identify the features of a transmission by its model number.
· Describe the major internal parts of an automatic transmission/transaxle.
· Describe the different designs of compound planetary gearsets.
· Name the major types of planetary gear controls used on automatic transmissions and explain their basic operating principles.
· Explain the purposes of seals and gaskets that are found in an automatic transmission/transaxle.
· Explain the purposes of engine and transmission/transaxle mounts. / Shop Manual Objectives
· Diagnose noise and vibration problems and determine needed repairs.
· Remove and install a transmission/transaxle assembly from a car or light truck.
· Disassemble, clean, and inspect a transmission/transaxle.
· Inspect, repair, and replace transmission case(s).
· Inspect and repair the bores, passages, bushings, vents, and mating surfaces of a transmission case.
· Inspect, repair, and replace extension housing bushings and seals.
· Inspect and replace speedometer drive gear, driven gear, and retainers.
· Inspect and replace external seals and gaskets.
· Assemble a transmission/transaxle after servicing it.
Overview
This chapter in both manuals covers the basic design differences and fitted equipment of the various common transmissions and transaxles. The chapters also cover the main components of a transmission. Removal, disassembly, inspection, reassembly, and installation of a transmission are also covered.
Reading Assignments
Classroom Manual, pages 117-144
Shop Manual, pages 205-239
Terms to Know
AnnulusBand
Butt-end seals
Composition gasket
Crocus cloth
Dowels
Dynamic seal
Gasket
Hard gasket / Hook-end seals
Lathe-cut seal
Lip seals
Open-end seals
O-rings
Planetary carrier
Planetary pinions
Ravigneaux gearset
RTV / Scarf-cut rings
Servo
Simpson gearset
Soft gasket
Square-cut seal
Static seal
Steel rings
Teardown
Toroidal
Lecture Outline and Notes
I. Objectives
Review the chapter’s objectives.
II. Basic Designs
Discuss and describe the various types of transmissions found in today’s vehicles.
A. Transmission versus Transaxle
Discuss the differences and similarities between a transmission and a transaxle; include a discussion on longitudinally mounted transaxles.
B. Housings
Discuss the construction of a housing with its parts and mechanical and electrical connections.
III. Diagnosis of Noise and Vibration Problems
A. Discuss vibration diagnosis.
B. Discuss noise diagnosis.
IV. Transmission/Transaxle Removal
Discuss transmission/transaxle removal preparation and removal procedures.
V. Transmission Case Service
A. Transmission Case Service
Discuss the need for cleaning passageways and performing a careful inspection.
B. Extension Housing
Describe the inspection of the extension housing.
C. Cracks
Discuss methods used to locate and repair cracks.
VI. Internal Components
Discuss the main components found in the inside of most automatic transmissions.
VII. Final Drives
Briefly discuss the types of final drive units found in today’s transaxles.
VIII. Disassembly
Discuss and demonstrate the general procedure for disassembling a transmission; emphasize the need for cleanliness and orderliness. Suggest that subassemblies be removed before they are disassembled. Also, mention that detailed discussions on these subassemblies are part of later chapters in this book.
IX. Gaskets and Seals
A. Gaskets
1. Discuss the use of gaskets on automatic transmissions.
2. Explain when an old gasket can be reused.
3. Explain the reason for retaining the old gasket.
4. Explain how to straighten the pan’s sealing surface.
B. Seals
1. Describe the use of seals in an automatic transmission.
2. Describe the square-cut seal, its uses, and its installation.
3. Discuss the use of lip seals and their installation.
4. Explain the purpose of sealing rings.
5. Describe open-end, butt-end, and locking rings.
6. Describe solid sealing rings, their purpose, and their removal and
installation.
X. Reassembly and Testing
A. Sub-Assemblies
Discuss the need for testing and measuring sub-assemblies.
B. Seal Installation
Discuss the inspection of every seal and gasket before installation.
C. Transmission Reassembly
1. Discuss the use of petroleum jelly during assembly to hold and
lubricate.
2. Describe general assembly procedures.
D. Reinstallation of the Transmission
Discuss the guidelines for reinstalling the transmission/transaxle.
E. After Installation
1. Discuss the initial checks prior to use.
2. Discuss the need for computers to relearn procedures.
3. Discuss methods for relearning.
XI. Speedometer Drive Service
Describe the need and methods for servicing speedometer drives.
XII. Mounts
Review the importance of engine and transmission mounts, especially since the transmission or transaxle must be removed for service and the mounts are removed or disconnected.
XIII. Summary
Review the material covered, emphasizing the main points and key words.
Chapter 5 Answers to Review Questions
CLASSROOM MANUAL, PAGES 144-146
Short Answer Essays
1. Current model number coding indicates the work capacity of the transmission, the number of forward gears, its directional placement in the vehicle, and whether it has electronic controls.
2. Transmission housings are cast to secure and accommodate: multiple friction disc assemblies, fluid passages, threaded bores and/or studs to fasten mounts, bores for the fluid level dipstick and filler tube, various threaded bores for a variety of sensors and switches, bores for gear selector attachment, fittings for the fluid cooling lines, mounting points for the pump and valve body, mounting for the oil pan, and round structures projecting from the side to serve as the cylinders for the servo and accumulator assemblies. Some housings have bores for the band adjusting screws.
3. There are two common designs of compound gearsets: the Simpson gearset, in which two planetary gearsets share a common sun gear, and the Ravigneaux gearset, which has two sun gears, two sets of planet gears, and a common ring gear.
4. The input shaft connects the output of the torque converter to the driving members inside the transmission. Each end of the input shaft is externally splined to fit into the internal splines of the torque converter’s turbine and the driving member in the transmission. Normally, the front clutch pack’s hub is the driving member. The output shaft connects the driven members of the gearsets to the final drive gearset. The rotational torque and speed of this shaft varies with input speed and the operating gear. On RWD vehicles, the output shaft is connected to the rear drive axle by the drive shaft.
5. A band is a braking assembly positioned around a stationary or rotating drum. The band brings a drum to a stop by wrapping itself around the drum and holding it. Connected to the drum is a member of the planetary gear train. The purpose of a band is to hold a member of the planetary gearset by holding the drum and connecting planetary gear member stationary.
6. Torrington bearings are thrust washers fitted with roller bearings. These thrust bearings are primarily used to limit end play but also to reduce the friction between two rotating parts. Most often Torrington bearings are used in combination with flat thrust washers to control end play of a shaft or the gap between a gear and its drum.
7. Chain-drive final drive assemblies use a multiple-link chain to connect a drive sprocket, connected to the transmission's output shaft, to a driven sprocket that is connected to the differential case. This design allows for remote positioning of the differential within the transaxle housing.
8. External and internal snap rings are used as retaining devices throughout the transmission. Internal snap rings are used to hold servo assemblies and clutch assemblies together and are available in several thicknesses so they can be used to adjust the clearance in multiple-disc assemblies. Some snap rings for clutch packs are waved to smooth clutch application. External snap rings are used to hold gear and clutch assemblies to their shafts.
9. The band is hydraulically applied by a servo assembly. The servo assembly converts hydraulic pressure to a mechanical force that applies a band to hold a drum stationary.
10. When two gearsets are in tandem, the front ring gear is normally connected to the rear carrier and the rear ring gear is connected to the front carrier.
Fill-in-the-Blanks
1. Separate casting, transmission housing
2. Bushings
3. Sprag, roller
4. Helical, planetary, hypoid, chain drive
5. Sun gear, planetary carrier, ring gear
6. Increased, decreased
7. O-ring, lip seal, square-cut seal
8. Butt-end, open-end, hook-end
9. Rubber, cork, paper, synthetic materials, plastic
10. Sun, planet, ring
Multiple Choice
1. A
2. C
3. D
4. C
5. C
6. A
7. B
8. C
9. C
10. C
SHOP MANUAL, PAGES 239-240
ASE-Style Review Questions
1. C
2. C
3. B
4. C
5. C
6. C
7. B
8. D
9. A
10. C
ASE Challenge Questions
1. A
2. A
3. C
4. C
5. A
Instructor’s Guide to Accompany Today’s Technician: Automatic Transmissions & Transaxles 3E 39