Gearbox Flashcards
What two categories of gearboxes are there?
Manuel and automatic
Which type of gearbox uses a torque converter?
Automatic gearbox
What is direct drive?
Where the output shaft is rotating at the same speed as the engine
What is another name for a countershaft?
Lay shaft
What gear would you be in if you were experiencing high torque and low speed?
1st gears
What are disadvantages of sliding mesh gearboxes?
- Excessive gear noise due to spur-type gear
- Difficulty in obtaining smooth, quick and quiet change of gear
What gearbox was introduced to overcome the disadvantages of the sliding mesh gearbox?
Constant mesh gearbox
How are helical gears correctly aligned in a constant mesh gearbox?
Thrust washers
What replaces the dog clutch in a synchromesh gearbox?
The synchroniser
What two main features are incorporated in the baulk ring synchromesh?
- Friction cone pressure, or load, is proportional to the speed of change
- An interception device prevents positive gear engagement until the speed of the two gears is equal
What are the 3 grooves on the hub of a synchromesh?
To locate the shifting plates
Why are slots on a baulk ring wider than the shifting plates?
To allow for a small amount of radial movement
What is a splitter gearbox?
A conventional 4 or 5 speed gearbox with additional gears to split the number of speeds in the main gearbox
What actuates a splitter gearbox?
A two position compressed air cylinder
What two ratios are in a splitter gearbox?
- Direct ratio (low)
- Indirect -ratio (high)
Does the range change gearbox change the input or output of the gearbox?
The output
What gear system does a range change gearbox use?
Epicyclic gear
How do you achieve a high and low range in a range change gearbox?
- High (everything locked together, sun gear drives directly)
- Low (annulus is clamped and planet gears crawl around the sun gear
How is a range change gearbox actuated?
An air piston operated by two solenoid valves (one for low and one for high)
What prevents changing from a high range gear to a low range gear in a range change gearbox?
A range change interlock determined by speed sensors
What is a power take off used for?
To send power to vehicles ancillary equipment
What safety precautions do you need to be aware of in a PTO?
- Limitations on engine/vehicle speed
- Excessive hydraulic pressures
- High speed rotating components
- Correct clutch operation
What is the primary role of a transfer gearbox?
To divide torque to all driven axles
What are additional roles of a transfer gearbox?
- Provide means of disconnecting the front or any axle from the drive line
- Using a suitable gear ratio to provide an increased torque to each axle
- House a third differential and lock
What methods of gear selection are there?
- Direct
- Remote (Rod and cable)
For reasons of safety, what must a manual gearbox include?
- Selector Detent
- Interlock Mechanism
What are two designs of an interlock mechanism?
- Swinging calliper
- Ball and plunger
What is the purpose of an interlock mechanism?
To prevent the engagement of two gears simultaneously
What does a start inhibit do on an automatic transmission?
Prevent the car from starting when not in ‘P’ and ‘N’
What is a ‘kick-down’ cable used for in automatic transmission?
To manually shift down a gear when needed
What does ECAT allow for?
- Rapid change to engine torque (improves performance)
- Better gear changes
- Improved emission control
What are advantages of ECAT?
- Multiple shift patterns (modes) available
- Driving modes stored on ‘shift maps’ in the ECU (lift)
Smoother gear shifts - Readily available for use in other vehicles
- Simplified hydraulic control system
How is semi automatic transmission defined?
A transmission in which some of the functions of the normal ratio changes are affected automatically
How many clutch packs are in a CVT?
2 - one for drive and one for reverse
What moves the secondary pulley back in a CVT?
Return spring in the pulley
