Service Diagnosis - Steering Gear And Pump; Variable Ratio Power Steering - Jeep 1979 CJ-5 Technical & Service Manual

2L-6
POWER STEERING GEAR AND
PUMP
¥ arlable Ratio P o v m r Stoning
A variable ratio power steering gear is used on Chero-
kee, Wagoneer and Truck models. CJ models are equip-
ped with a constant ratio steering gear.
The ratio of a steering gear is the relationship of
steering wheel movement to that of the front wheels. It
is described in terms of the number of degrees of steer-
ing wheel rotation required to turn the front wheels one
degree.
Variable ratio steering is accomplished by using a
pitman shaft sector that has one long center tooth
flanked by two short sector teeth. This is opposed to a
constant ratio gear where all sector teeth are of equal
length (fig. 2L-5). Because the variable ratio gear has
unequal length sector teeth, companion changes are also
made in the rack piston teeth (fig. 2L-5).
Since the sector is basically a series of levers, any
movement of the rack piston causes the sector to swing
the pitman arm in the same ratio. In other words, it
turns the pitman arm the same number of degrees with
each sector tooth.
To increase or decrease steering ratio, it is only neces-
sary to change the length of the sector teeth. A low
numerical ratio (smaller radius sector with shorter
teeth) produces greater pitman arm movement than
would a high ratio sector with longer teeth and greater
leverage.
On this basis, the variable ratio sector is in reality one
long, high ratio lever at the center, flanked by two lower
ratio levers for left and right turns.
In the straight ahead position, only the tip of the long
center tooth is in contact with the rack piston. As a
result, initial movement of the rack piston in either
direction produces a relatively small response of the
sector and pitman arm. This is due to the high ratio
produced by a long lever relationship.
Service Diagnosis—Steering Gear and Pump
Condition Possible Cause
Correction
HISSING NOISE IN
(1)
There is some noise in all power (1) Slight hiss is normal and does
STEERING GEAR
steering systems. One of the
not affect steering.
most common is a hissing sound
most evident at standstill park-
ing. There is no relationship
between this noise and per-
formance of the steering. Hiss
may be expected when steer-
ing wheel is at end of travel
or when slowly turning at
standstill.
RATTLE OR CHUCKLE
(1)
Gear loose on frame.
(1)
Tighten gear-to-frame mounting
NOISE IN STEERING
(1)
bolts.
GEAR
60702A
Because of this relationship, the steering ratio re-
mains a nearly constant 16:1 for the first 40 degrees of
steering wheel movement in either direction from
center.
Turning the steering wheel further reduces the length
of the lever. This moves the point of contact down the
side of the center tooth decreasing the radius.and pro-
viding a steering ratio of 13:1 at full lock.
C O N S T A N T R A T I O V A R I A B L E R A T I O
AJ41064
Fig. 2L-5 Rack and Sector Comparison
SERVICE DIAGNOSIS
When diagnosing suspected power steering system
malfunctions, refer to the Service Diagnosis Charts in
this section for probable causes and indicated repair
procedures.
To avoid ineffective or unneccessary repair, do not
attempt to correct a malfunction until an accurate diag-
nosis has been made. Utilize the diagnosis charts, hy-
draulic pressure test and leak diagnosis procedures
before servicing the gear or pump.