Chevrolet 70 Series 1970, Service Manual

Page: 186 / 841

FRONT SUSPENSION 3-3
not return to the norm al operating p osition due to
the tir e s gripping the flo o r su rfa ce when the v e ­
h icle is low ered on the jack.
IMPORTANT: "TOE-IN" MEASUREMENTS
MUST BE MADE AT THE HORIZONTAL AXIS OF
THE WHEEL.
"Toe-in" is co rrected by loosening clam p bolt
at tie rod ends, then turning tie rod with pipe
wrench until w h eels have proper to e -in .
NOTE: On v e h ic le s with pow er steerin g , loosen
pow er c y lin d e r - t o - t ie rod bracket U -bolt nuts.
With both tie rod ends in sam e plane, tighten
clam p bolts se c u r e ly . T o e-in should be 1 /8 to 1 /4
inch except on F E -970 a x le . See "Alignment Speci­
fic a tio n s.”
With pow er ste e r in g , tighten pow er cy lin d er-
to -tie r o d bracket U -b olt nuts. Adjust power cy lin ­
der a s d irected in "POWER STEERING" (SEC. 9B)
of th is manual.
FRONT WHEEL CAMBER
Cam ber is the amount in inches or d eg rees
that front w h eels a re tilted outward at top from
v e r tic a l p osition (s e e "A," fig . 1). Cam ber o ffse ts
w heel deflection, due to w ear of front axle p a rts,
and p reven ts a r e v e r s e or negative cam ber condi­
tion. A r e v e r se or negative cam ber is an inward
inclination of w h eels at the top.
If cam ber is extrem e or unequal betw een
w h eels, im proper ste e r in g and e x c e s s iv e tir e w ear
w ill resu lt.
Cam ber variation s may be caused by w ear at
w heel b earin gs and ste e r in g knuckle bushings, or
by a bent ste er in g knuckle or a x le center.
Sp ecification s are lis te d at rea r of th is sectio n .
NOTE: The Tim ken F E -9 7 0 axle a s u sed on
so m e v e h ic le s is of the centerpoint ste e r in g type
and has only a very slig h t cam ber dim ension.
CHECKING AND CORRECTING CAMBER
B efo r e checking cam ber, check w ear at king
pins a s follow s:
Jack up front of v e h ic le , p u ll bottom of w heel
outward and take a cam ber reading; then pull top
of w heel outward and take a cam ber reading. If
readings vary m ore than % , make follow ing ad­
justm ents:
1. Adjust the w heel b earings as d irected in
"FRONT HUBS AND BEARINGS" (SEC. 3D), then
take cam ber readings a s shown on chart (fig.
1
).
If readings s t ill vary over X°, rep lace stee rin g
knuckle bushings and king pins as in stru cted in
"FRONT AXLE" (SEC. 3B).
2. Check the w heel run-out as in stru cted in
WHEELS AND TIRES (SEC. 10) of this manual. If
run-out is e x c e s s iv e , straighten or rep lace w heel.
3. P la c e v e h ic le on le v e l su rfa ce , with norm al
Figure 2 —Method of Checking Frame Angle
w eight of v e h ic le on w h eels, then take final cam ber
reading. If cam ber gauge is not availab le, readings
can be taken as shown on chart in figure
1
.
Camber may be checked using a la r g e square
and p rotractor, as follow s:
Scribe a lin e fro m cen ter point of p rotractor
to top of square on c o r r e c t d egree of angle a s de­
term in ed from sp ecifica tio n s at end of th is sectio n .
P la c e sq u are on flo o r adjacent to cen ter of
w heel a s shown in figu re 1. M easure distan ce b e­
tw een sc r ib e d lin e on square and w heel r im s at
top and bottom . If readings taken a re both iden­
tic a l, cam ber is c o r r e ct. If readings differ, s t e e r ­
ing knuckle bushings are worn o r a x le cen ter is
bent. The knuckle a lso may be bent. Cam ber di­
m ensions of right w h eel should not vary over 3 /3 2 -
inch from cam ber dim en sion s of le ft w heel.
4. To determ ine which part is bent, check
king pin inclination (B, fig . 1). If kingpin inclination
i s co r r e ct, then ste e r in g knuckle is bent. Method
of checking kingpin inclination without u se of in ­
strum ents is d escrib ed u n d er "King Pin Inclination"
la te r in th is sectio n .
AXLE CASTER
P o sitiv e c a ste r is the rearw ard tilt from the
v e r tic a l of the kingpin. N egative or r e v e r s e ca ste r
is the forw ard tilt from the v e r tic a l of the kingpin.
In correct c a ste r may resu lt from sagging
sp rin g s, bent a x le, tw isted axle, o r uneven tighten­
ing of spring U -bolt nuts. Tighten a ll U -bolt nuts
equally. R efer to "FRONT SPRINGS" (SEC. 3C )for
U -bolt torque sp e c ific a tio n s. G enerally, if the axle
is tw isted , the c a ste r w ill be unequal for right and
left sid e .
CHECKING AND CORRECTING CASTER
IMPORTANT: C aster, cam ber, and to e -in d i­
m ensions are for v eh icle carrying its design load
w hereby the fram e in m ost in sta n ces would be
le v e l. If alignm ent check is to be made with fram e
NOT LEVEL the fram e angle (fig. 2) m ust be de­
term in ed and added to the c a ste r angle to obtain a
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCKSHOP MANUAL