1. Chapter 7 Light vehicle drivelines
Tutor notes
Aim: To show the function and operation of light vehicle driveline and transmission system units and components.
Objective: At the end of this presentation, learners will be able to describe the purpose and operation of light vehicle driveline and transmission units and components.

2. Torque convertor or clutch
Drive wheels
Transmission layout
Differential
Universal joints
Engine
Prop shaft
Transmission
Tutor notes
Begin with an overview of a standard transmission layout, showing how each component is linked to the other and transmits drive from the engine to the road wheels.
Torque convertor or clutch

3. Components of a friction clutch
Tutor notes
Show the components of a friction clutch.
Ask learners to name each component of the friction clutch.

4. Clutch operating mechanism – cable operation
Clutch release cable
Clutch cover
Release fork
Clutch pedal
Tutor notes
Explain the operating mechanisms of friction clutch systems.
Describe the advantages and disadvantages of cable operated systems. If appropriate take learners into the workshop and show the operating mechanism in action.

5. Clutch operating mechanism – hydraulic system
Master cylinder
Clutch cover
Flexible hose
Release fork
Clutch pedal
Release cylinder
Tutor notes
Explain the operating mechanisms of friction clutch systems.
Describe the advantages and disadvantages of hydraulically operated systems. If appropriate take learners into the workshop and show the operating mechanism in action.

6. Friction plate Tutor notes
Describe the construction of the clutch friction/drive plate. Show the friction material, cushion springs, torsional springs and centre hub. If possible hand a friction plate around the class so that the different sections can be seen.

7. Torque converter Outer housing Turbine Stator Impeller Tutor notes
Ask learners the meaning of the word ‘hydraulics’.
Answer – the science of movements of liquids. As liquids are virtually incompressible they can be used to operate mechanisms.
Explain the function of the components found inside a torque converter. Describe how fluid is taken into the impeller, and thrown outwards into the blades of the turbine by centrifugal force. Upon leaving the turbine, fluid strikes the blades of the stator then turns the impeller at speed multiplying torque.

8. The need for a gearbox Increased torque Torque conversion mechanism
Tutor notes
Ask learners why a car needs a gearbox.
Answer – to multiply the torque or turning effort produced by the engine, so that it is usable under many different driving conditions.

9. The need for torque multiplication
More torque
Torque multiplier
Torque
Tutor notes
Show how torque and leverage can be multiplied by using gears.

10. Gears, ratios and direction
Driven gear
Idler gear
Driver gear
Driven gear
Tutor notes
Explain the principle of gear ratios – when a small drive gear operates a large driven gear, speed is reduced and torque is multiplied. When a large drive gear operates a small driven gear, speed is increased and torque is reduced.
Ask learners to calculate gear ratios from simple given values.
Describe the function and operation of an idler gear. Explain that this gear has no effect on overall gear ratio, but merely serves to change the direction of rotation and this is how reverse gear is achieved.

11. Gear types Spur gears Helical gears Tutor notes
Describe the differences between spur and helical gears and the advantages and disadvantages of each.
Spur gears act directly and create low amounts of drag, which helps improve overall performance, but can make them noisy in operation. A spur-cut gear can be slid in and out of mesh with another spur-cut gear making them useful as a reverse gear idler.
A helical-cut gear has teeth on an angle as shown in the illustration. This means the teeth are not just cut on a diagonal; If they were extended around a cylinder they would actually be shaped like that of a coil spring. Helical-cut gear teeth provide a large surface area making them very strong, less prone to wear and quiet in operation. Unfortunately due to the design and shape of a helical-cut gear they cannot be slid in and out of mesh. This means they have to be used in a gearbox known as a ‘constant-mesh’.
Spur gears
Helical gears

12. Detent mechanism Neutral position Gear engaged Selector rod
Spring loaded ball
Selector rod
Neutral position
Gear engaged
Tutor notes
Explain that when a gearbox is in operation, thrust from the gear teeth is trying to disengage them. Describe how a detent mechanism operates and helps to keep a selected gear in position.
Use a ratchet and socket attachment to show how a detent works (it is similar to how a socket is kept on the end of a ratchet).

13. Gear selection and interlock
Selector forks
Selector rod
Detent
Gear lever
Selector hub
Neutral position
Locked
Free
Tutor notes
Gears within a gearbox are turning at different speeds; ask learners what would happen if two different gears were selected at the same time.
Answer – the gearbox would lock up and be unable to turn.
Describe the process of using an interlock mechanism to prevent two gears being selected at the same time.
Gear selection mechanism
Interlock mechanism

14. Selector hub Synchroniser Selector hub Dog teeth Gear
Detent
Friction surfaces
Dog teeth
Tutor notes
Describe the operation of a selector hub.
Describe the operation of the synchroniser and why a baulk ring mechanism needs to be added to improve gear selection. State how the grooves on the inside of the baulk ring are designed to cut through the surface tension of the lubrication oil to provide grip in the form of a friction clutch.
If possible, hand a dismantled synchromesh mechanism around the class, so learners are able to see the different parts.

15. Drive layouts – front-wheel drive
Engine
Clutch
Transaxle
Differential
Drive shaft
Tutor notes
Describe front-wheel drive layout.
Ask learners to sketch the drive layout and investigate vehicle manufacturers and types of vehicle which use this drive system.

16. Drive layouts – rear-wheel drive
Engine
Clutch
Propeller shaft
Rear axle shaft
Differential
Transmission
Tutor notes
Describe rear-wheel drive layout.
Ask learners to sketch this drive layout and investigate vehicle manufacturers and types of vehicle which use this drive system.

17. Drive layouts – four-wheel drive
Engine
Driveshaft
Propshaft
Transaxle
Centre differential
Front differential
Rear differential
Clutch
Tutor notes
Describe four-wheel drive system.
Ask learners to sketch this drive layout and investigate vehicle manufacturers and types of vehicle which use this drive system.

18. Prop shafts – movement Rear axle Difference between arcs
Transmission
Propeller shaft
Rear axle
Difference between arcs
Rear axle swing arc
Propeller shaft swing arc
Tutor notes
Explain why universal joints (see next slide) are required when used with prop shafts. Describe the process of cyclic variation (speeding up and slowing down of the prop shaft), if the universal joints at either end of the prop shaft are not synchronised.

19. Prop shafts – universal joints
Spider
Yoke
Circlip
Bearing cup
Sleeve (slip joint)
Tutor notes
Connect a universal joint from a socket set to a ratchet and socket.
Ask learners to undo a bolt at an angle so they can feel the speeding up and slowing down.
Universal joints

20. Constant Velocity (CV) joints
Steel ball
Drive shaft
Ball cage
Outer race
Inner race
Drive axis
Driven axis
Tutor notes
Explain to learners why constant velocity joints are required on front- wheel drive vehicles, i.e. due to the nature of front suspension movement and steering operation, universal joints would be unsuitable due to the speed variation created.
Ask learners what would happen if the constant velocity drive shaft gaiter becomes split.
Answer – lubrication grease would leak from the constant velocity joint, leading to rapid wear and noise.
Explain the process of checking for noise on a constant velocity joint.