[ Pobierz całość w formacie PDF ]
Z
STEERING 19 - 1
STEERING
CONTENTS
page
page
AUTOMATIC TRANSMISSION SHIFTER/
IGNITION INTERLOCK MECHANISM ......
GENERAL INFORMATION ..................
POWER STEERING PUMP .................
POWER STEERING SYSTEM DIAGNOSIS .....
RECIRCULATING BALL POWER STEERING
GEAR ...............................
STEERING COLUMN .....................
STEERING LINKAGE .....................
TORQUE SPECIFICATIONS ................
GENERAL INFORMATION
STEERING SYSTEM COMPONENTS
Power steering systems use the following (Fig. 1);
²
Rotary valve assembly
²
Steering worm shaft
²
Recirculating-ball steering gear
²
Rack piston assembly
²
Steering linkage
Pitman shaft
The movement of these parts, while turning or
parking, is aided by hydraulic pressure and flow sup-
plied by the pump. Manual steering is always avail-
able at times when the engine is not running or in the
event of pump or belt failure. Steering effort is higher
under such conditions.
The steering stub shaft, rotary valve, worm shaft,
and rack piston assembly are all in line. All oil pas-
sages are internal within the gear housing except for
the pressure and return hoses between the gear and
the pump.
The power steering gear has a recirculating ball
system. This acts as a rolling thread between the
worm shaft and rack piston. The worm shaft is sup-
ported by a thrust bearing at the lower end and a
bearing assembly at the upper end. When the worm
shaft is turned right, the rack piston moves up in
gear. Turning the worm shaft left moves the rack
piston down in gear. The rack piston teeth mesh with
the sector, which is part of the pitman shaft. Turning
the worm shaft turns the pitman shaft, which turns
the wheels through the steering linkage.
The control valve in the steering gear directs the
power steering fluid to either side of the rack piston.
The rack piston is assisted by hydraulic pressure. If
the steering system loses hydraulic pressure, the ve-
hicle can be controlled manually, but with higher
steering effort.
An identification code located on the side cover
designates the gear ratio (Fig. 2).
²
Belt driven hydraulic steering pump with fluid res-
ervoir
²
Pump pressure and return hoses and fittings
²
Steering column with shifter interlock
²
Intermediate shaft between column and gear
Fig. 1 Power Steering Systems
POWER STEERING GEAR
The steering gear is mounted on the left frame rail.
The gear is joined to the intermediate shaft by a
universal joint coupling. The coupling helps isolate
noise and road shock from the interior.
The major internal components of the gear are the:
Code AL designates 12.7:1 ratio without Trailer
Tow
²
Code MN designates 12.7:1 ratio with Trailer Tow
Trailer Tow gears have higher temperature resis-
tant seals. Otherwise gears are interchangeable.
²
²
 19 - 2 STEERING
Z
The power steering pump is connected to the steer-
ing gear via high pressure and return hoses. The
pump shaft has a pressed-on drive pulley that is belt
driven by the crankshaft pulley (Fig. 3).
CAUTION: Vehicles equipped with H.D. Trailer Tow
Package use high temperature seals in the power
steering pump. The pumps are identified with a YEL-
LOW label attached to the back of the reservoir. Use
ONLY the correct seal kit when servicing the steer-
ing pump with this identification.
Fig. 2 Ratio Code Location
CAUTION: Vehicles equipped with H.D. Trailer Tow
Package use high temperature seals in the power
steering gear. The gears are identified with a YEL-
LOW paint mark. The mark is on the pitman shaft
side of the housing below the side cover. Use ONLY
the correct seal kit when servicing the steering gear
with this identification.
A recirculating ball steering gear is used with the
power (assisted) steering system (Fig. 1). The power
steering gear can be adjusted and internally serviced.
STEERING LINKAGE
The steering linkage consists of a pitman arm, drag
link and tie rod. Adjustment sleeves are used on the
tie rod and drag link for toe and steering wheel
alignment. Refer to Group 2, Front Suspension and
Axles for wheel alignment information.
Fig. 3 TC-Series Pump
POWER STEERING PUMP
Hydraulic pressure is provided for operation of the
power steering gear by a belt driven power steering
pump. The power steering pump is a constant flow
rate and displacement, vane-type pump. The internal
parts in the housing operate submerged in fluid. The
flow control orifice is part of the high pressure line
discharge fitting. The pressure relief valve inside the
flow control valve limits the pump pressure.
Power steering pumps have different pressure
and flow rates. They are not interchangeable
with pumps installed in other vehicles.
STEERING COLUMNS
Two general types of steering columns are installed
on Grand Cherokee vehicles: a fixed, non-tilt column
and a tilt column. The multi-position, tilt column is
optionally available.
The column to gear intermediate shaft is equipped
with universal joints. Rubber isolators are built into
the shaft to absorb noise and vibration from the steer-
ing system.
Both types of steering columns have anti-theft pro-
visions. They are energy-absorbing (collapse from im-
pact in the event of a front end collision).
Z
STEERING 19 - 3
POWER STEERING SYSTEM DIAGNOSIS
HISS NOISE COMPLAINT
There is some noise in all power steering systems.
One of the most common is a hissing sound most
evident at stand still parking. Hiss is a high fre-
quency noise similar to that experienced while slowly
closing a water tap. The noise is present in every
steering gear valve and results from high velocity
fluid passing valve orifice edges. There is no relation-
ship between this noise and performance of the steer-
ing. HISS MAY BE EXPECTED WHEN SLOWLY
TURNING AT STANDSTILL. The noise transmission
of this into the passenger compartment is controlled
by the use of the universal joint coupling. There is a
rubber isolator in the steering coupling (intermediate)
shaft to muffle hiss. If hiss is extremely objectional,
replace the shaft. If hiss is persistent, service the
steering gear.
Fig. 1 Pressure Test Gauge
POWER STEERING PUMP PRESSURE TEST
(1) Check belt tension and adjust as necessary.
(2) Disconnect high pressure hose at gear or pump.
Use a container for dripping fluid.
(3) Connect Gauge 7617 (J21567) to both hoses us-
ing adapter fitting (Fig. 1). Connect spare pressure
hose to gear or pump.
(4) Open the test valve completely.
(5) Start engine and let idle.
(6) Check fluid level, add fluid as necessary.
(7) Gauge should read below 862 kPa (125 psi), if
above, inspect the hoses for restrictions and repair as
necessary. The initial pressure should be in the range
of 345-552 kPa (50-80 psi).
must be above specifications and within 345
kPa (50 psi) of each other.
²
Pressures within 345 kPa (50 psi) of each other but
below specifications, replace pump.
CAUTION: Do not force the pump to operate against
the stops for more than 2 to 4 seconds at a time or
pump damage will result.
(9) Open the test valve, turn steering wheel ex-
treme left and right positions against the stops.
Record the highest indicated pressure at each posi-
tion. Compare readings to specifications. If highest
output pressures are not the same against either
stop, the gear is leaking internally and must be re-
paired.
The steering pump relief pressure is 1400 p.s.i.
CAUTION: The following test procedure involves
testing maximum pump pressure output and flow
control valve operation. Do not leave valve closed
for more than 5 seconds as the pump could be
damaged.
6
50.
(8) Close valve fully three times and record highest
pressure indicated each time.
All three readings
Pressures above specifications but not within 345
kPa (50 psi) of each other, replace pump.
²
 19 - 4 STEERING
Z
POWER STEERING SYSTEM DIAGNOSIS
Z
STEERING
19 - 5
POWER STEERING SYSTEM DIAGNOSIS
[ Pobierz całość w formacie PDF ]