Chapter 77 Review Flashcards
Review of points in chapter 77
What are the functions of a steering system?
- Provide precise control of the front-wheel direction and, sometimes, the rear-wheel direction
- Maintain correct amount of effort needed to turn the wheels
- Transmit road feel to the driver’s hands
- Absorbs most of the shock going to the steering wheel from bumps
- Allows suspension action with minimal effect on the direction and alignment of the front wheels
What are the two basic kinds of steering systems used today?
- Linkage (worm gear)
- Rack-and-pinion
What kind of vehicles are linkage steering systems found?
Large, full-size pickup trucks and full-size vans, both two- and four-wheel drive
What kind of vehicles are rack-and-pinion steering systems found?
Passenger cars and small trucks for being lighter
List the components of a basic linkage (worm gear) steering system
- Steering wheel
- Steering shaft
- Steering column
- Steering gearbox
- Steering linkage
- Ball sockets
List the components of a basic rack-and-pinion steering system
- Steering wheel
- Steering column
- Steering shaft
- Steering pinion gear
- Rack
- Gear housing
- Tie-rods
What makes up the steering column assembly?
The steering wheel, the steering shaft, column (outer housing), and sometimes, ignition key mechanism, a flexible coupling, and a universal joint
Where is the steering column bolted?
It’s normally bolts to the underside of the dash
What is the assembly of the steering shaft to the column and the steering wheel then to the shaft?
Bearings fit between the steering shaft and the column. They let the shaft rotate freely. The steering wheel is splined to the shaft. A large nut holds the steering wheel on the shaft splines. The airbag is fastened to steering wheel
Where are the ignition lock and switch mechanism usually mounted?
The steering column in most vehicles, with the ignition lock normally on the top right-hand side of the column and the switch usually is bolted inside the steering column
What feature was implemented in late-model vehicles, in regards to steering, to prevent theft?
A locking steering wheel
Explain a common method of locking a steering wheel
A rack and a sector are used to slide a steel pin into mesh with slotted disc that is splined to the steering shaft. This locks the steering shaft to the column, preventing the steering wheel from being turned
What is the purpose of a collapsible steering column?
To help prevent driver chest and face injury during an accident
What are the different types of collapsible steering columns and how many pieces make it up?
- Steel mesh (crushing) columns
- Tube-and-ball (sliding) columns
- Shear capsule (break and slide) columns
In all types, the column is made up of two pieces
What is the purpose of a tilt steering column/tilt steering wheel?
To use a flex joint, or U-joint, to allow the top half of the column and the steering wheel to be positioned at different angles
What are the different types of tilt steering columns and their design?
- Manual tilt column uses a lever on the steering column to unlock the flex joint so the wheel can be moved up or down
- Power tilt column uses a small electric motor, a control switch, and a gear mechanism to change steering wheel angle and height
- Memory tilt wheels use a tilt control module (computer) to “remember” more than one steering wheel position. A sensor in the steering column provides feedback on the wheel’s position. When the switch is pressed, the control module energizes the power tilt motor to move the wheel to the pre-programmed position
In what type of steering system is the recirculating-ball gearbox used, linkage (worm gear) or rack-and-pinion?
Linkage (worm gear). Only linkage steering systems use a steering gearbox
What happens in a recirculating-ball gearbox?
It has small steel balls that circulate between the gear members
What are the components of a recirculating-ball gearbox?
- Worm shaft
- Sector shaft
- Ball nut
- Ball guides
- Adjusting nut
- Adjusting screw
- Gearbox housing
- End cover
What is the role of a worm shaft in a recirculating-ball gearbox?
Is the input gear connected to the steering column shaft. The balls fit and ride in the grooves in the worm gear. It is mounted in either ball bearings or roller bearings
What is the role of a sector shaft in a recirculating-ball gearbox?
Is the output gear from the steering gearbox. It transfers motion to the steering linkage. A sector gear is machined on the inner end of the sector shaft. It is mounted on anti-friction bearings
What is the role of a ball nut in a recirculating-ball gearbox?
It rides on the ball bearings and the worm gear. Grooves are cut in the ball nut to match the shape of the worm gear. The ball nut cannot rote, it slides up and down as the worm gear rotates
What is the role of ball guides in a recirculating-ball gearbox?
They route extra ball bearings in and out from between the worm and ball nut
What is the role of a bearing adjusting nut in a recirculating-ball gearbox?
Is usually provided to set worm shaft bearing preload
What is the role of an adjusting screw in a recirculating-ball gearbox?
Is used to set the sector shaft clearance
What is the role of the gearbox housing in a recirculating-ball gearbox?
Provides enclosure for the other components. Seals press into it to prevent lubricant leakage at the worm and sector shaft. Shaft bearings press into it as well. It is bolted to the vehicle frame or a reinforced area
What is the role of the end cover in a recirculating-ball gearbox?
Normally bolts on the housing to cover the end of the sector gear. It can be removed for gearbox service
What is gearbox/steering ratio?
Also called steering gear reduction. It’s a comparison between steering wheel rotation and sector shaft rotation
What is the range of gearbox ratios?
15:1 to 24:1
Which type of gearbox has a high gearbox ratio and why?
A manual gearbox will have a high gearbox ratio to reduce the amount of effort needed to turn the steering wheel
Which type of gearbox has a low gearbox ratio and why?
Power steering gearboxes so that turning front wheels requires less steering wheel rotation for faster steering response
What is the purpose and benefits of a variable-ratio gearbox?
It changes the internal gear ratio as the front wheels are turned from the center position. Most modern recirculating-ball gearboxes use variable-ratio design.
It is faster when cornering, requiring fewer turns to move the steering wheel from full right to full left. Also provides better control and response when maneuvering
What is the purpose of a constant-ratio gearbox?
It has the same gear reduction from full left to full right than variable-ratio gearbox. The sector gear teeth are the same length
What is a worm-and-roller gearbox?
It contains a roller that is mounted on the pinion shaft and meshes with the worm gear. The roller replaces the ball bearings and the ball nut used in the recirculating-ball gearbox. It imparts a rotary force on the pitman shaft as the worm gear rotates. This design reduces internal friction
What is steering linkage?
It’s a series of arms, rods, and ball sockets that connect the worm-type steering gearbox to the steering knuckles