508 Auto Fundamentals
to move from full left to full right, the easier the
steering. The modern steering gear ratio is a com-
promise between steering ease and handling.
Power Steering
Power steering is designed to reduce the
effort needed to turn the steering wheel by
using hydraulic pressure to bolster (strengthen)
the normal torque developed by the steering
gear. Power steering systems should ease steer-
ing wheel manipulation and, at the same time,
offer enough resistance that the driver can retain
some road feel. Power steering is used with both
conventional and rack-and-pinion systems. Both
types of power steering systems are discussed
in the following sections.
Ball nut
Clamp
Bolt
Nut
Adjuster
Shim
Bushing
Seal
Sector
shaft
Bushing
Nut
Cup
Seal
Bearing roller
Worm shaft
Ball nut and balls
Filler plug
Sector
Plug
Bearing
Roller
cup
Adjuster
Clamp
Screw head
Screw
threads
(worm shaft)
Nut (ball nut)
A
B
Gasket
Worm shaft
Figure 25-19.
Recirculating ball worm and nut steering gear. A—A simple steering gear action produced from a screw and nut. By turning
the screw, the nut (ball nut) will travel one direction or the other on the threads of the screw (worm shaft). This changes the
steering wheel’s rotary (around-and-around) motion into a lateral (side-to-side) movement of the steering linkage.
B—Cross-sections of the recirculating ball worm and nut steering gear. Study part names, locations, and functions.
Dodge; FMC Corp.
Road Feel
Road feel is the feeling imparted to the
steering wheel by the wheels of a vehicle in
motion. This feeling is very important to the
driver in sensing and predetermining vehicle
steering response.
A good driver can tell when the front
wheels are approaching the walk (slipping side-
ways) point and if more or less turning effort is
required to stabilize the vehicle body on turns
or when driving in windy conditions. Complete
and effortless power steering would rob the
driver of valuable road feel. To maintain road
feel, power steering systems require some wheel
effort. Wheel effort of approximately 1 to 9 lbs
pull on the steering wheel rim is acceptable.