Chevrolet 1977 light duty truck Service Manual page 201

CONDITION
Rattle or Chuck in Steering Gear.
Poor Returnability
POSSIBLE CAUSE
Insufficient or improper lubricant
in steering gear.
Pitman arm loose on shaft or
steering gear mounting bolt loose.
Loose or worn steering shaft
bearing.
Excessive over-center lash or
worm thrust bearings adjusted
too loose.
NOTE: On turns a slight rattle
may occur, due to the increased
lash between ball nut and pitman
shaft as gear moves off the center
of "high point" position. This is
normal and lash must not be
reduced to eliminate this slight
rattle.
Steering column misaligned.
Insufficient or improper lubricant
in steering gear or front suspension.
Steering gear adjusted too tight.
Front wheel alignment incorrect
(Caster)
CORRECTION
Add lube specified.
Tighten to specified torque.
Replace steering shaft bearing.
Adjust steering gear to specified
preloads.
Align column.
Lubricate as specified.
Adjust over-center and thrust
bearing preload to specifications.
Adjust to specifications.