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Section 121—-Adjustments
9
Chapter
I
STEERING
GEAR
Section
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121
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122
Inspection and Repair...
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123
Assembly...
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124
The steering system includes the steering gear, steering wheel,
and steering drag links between the pitman arms and the front axle
spindle arms. The steering gear is of the recirculating ball bearing
worm and nut type. Anti-friction steering is achieved by steel balls
which serve as rolling contacts between the worm and nut.
Rotation of the steering tube shaft moves the ball nut along the
worm. The left steering sector engages the rack on the ball nut, and
is thereby rotated through an arc by the movement of the ball nut
(fig. 2). The right sector engages the left sector and rotates the same
number
of degrees in the opposite
direction.
The
pitman
arms
transfer the motion of the sector to the spindle arms through
the
drag links.
121. ADJUSTMENTS.
When the wheels are in the straight ahead position, all backlash
should be removed, but if the wheels are turned to the extreme right
or left, a slight backlash will be present due to the gear tooth design.
This characteristic permits a backlash adjustment for wear between
the worm
nut teeth and the sector gears in the much
used center
position without causing binding or tightness in less used portions
of the sector gears and worm nut,
Steering gear adjustments may be checked before removing the
unit from the tractor or disassembling the unit. Adjusting the steer-
ing gear on the tractor in many cases will eliminate excessive back-
lash caused by improper adjustment between the sectors and the
ball nut.
To determine
the cause
of excessive
backlash,
first check the
adjustment of the steering tube bearings. Disconnect the drag links
from the pitman arms. Turn the steering wheel to the right or left
to the end of its travel, then back about 14 turn. Measure the force
required to rotate it by use of a spring scale attached to the rim
(fig. 7). If a force from 14'to 114 pounds will maintain the wheel in
3730-47
§ 121.
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