Chevrolet 70 Series 1970, Service Manual

Page: 189 / 841

FRONT SUSPENSION 3-6
FRONT AXLE
R eferen ce is made to axle m odels in th is s e c ­
tion. Specifications are lis te d at the end of this
sectio n for each axle m odel. For truck s e r ie s
application, r efer to "Model Data" at the front of
this manual.
A xle steerin g knuckles are constructed as
shown in fig u res 1, 2, and 3. Wheel bearin gs,
sp rin g s, steerin g , and brake parts which a re mount­
ed on front axle a re d escrib ed in their r e sp ectiv e
sectio n in th is manual.
FRONT AXLE CONSTRUCTION
Front axle center se c tio n is o n e-p iece ste e l
forging with I-beam se ctio n in which dowel pins
are in stalled to lo ca te spring s e a ts . Outer ends of
axle center a re m achined to accom m odate stee rin g
knuckles and king p in s.
The centerpoint steer in g type axle (FE -970)
(fig. 3) is used on so m e m od els. The term "center­
point steerin g type" in d icates that king pin pivot
point is in d irect lin e w ith center of tir e .
Figure 1 —Steering Knuckle Construction (Corp. F070 Axle)
A stra ig h t-ty p e king pin is em ployed and is
retained to the a x le cen ter with two tapered draw
k ey s. A flat m etal cap and a gask et, which are
secu red to top of knuckle with two s c r e w s , prevent
dust and m oistu re from entering the upper bushing.
A snap ring retained expansion plug s e r v e s the
sam e purpose at knuckle low er bushing.
The v e r tic a l thrust load on front axle i s c a r ­
ried on r o lle r -ty p e sh ield ed bearing located b e­
tw een the axle cen ter and low er portion of each
knuckle.
P e r io d ica lly check ste erin g knuckle bushings
for w ear and a lso check the k n u ck le-to -a x le center
draw k eys for lo o s e n e s s . O v e r siz e (taper only)
draw k eys are availab le if the k ey s should b ecom e
lo o se and the h oles enlarged. R efer to fig u re 4.
NOTE: The sh o rter draw key is u sed in the
upper position .
Check the v e r tic a l m ovem ent of knuckle in
relation to axle cen ter. If m ovem ent ex c e e d s 0.005"
add one or m ore s e r v ic e sh im s betw een axle cen­
te r and upper portion of knuckle. Shim s a re a v a il­
able in 0.005", 0.010" and 0.015" th ick n ess.
FRONT AXLE GENERAL
MAINTENANCE
F ollow ing m aintenance operations should be
perform ed at in terv a ls determ ined by se v e r ity of
se r v ic e :
1. Inspect sp rin g U -b olts for tig h tn ess. If
lo o se , tighten a s d irected in "FRONT SPRINGS"
(SEC. 3C) la ter in this group.
2. Tighten ste erin g arm and tie rod end stud
nuts to torque sp e c ifie d in STEERING SYSTEM
(SEC. 9) of th is manual.
3. Lubricate front axle p a rts as in stru cted in
LUBRICATION (SEC. 0) of th is manual. When lub­
ricating front axle p a r ts, o b serv e condition of s e a ls
at tie rod ends. If s e a ls a re found to be dam aged
or m issin g , new s e a ls should be in sta lled im m ed ­
ia te ly . R efer to STEERING SYSTEM (SEC. 9).
4. Exam ine ste e r in g knuckle bearing caps for
tig h tn ess and evidence of lubricant leak age. Tighten
o r rep lace p arts a s required with genuine GMC
rep lacem en t p a r ts.
5. On F -0 7 0 Corporation axle, in sp ect and
tighten king pin draw key nuts. L o o se draw keys
w ill perm it king pin to turn in axle cen ter, thus
enlarging king pin h ole. If hole b eco m es too greatly
enlarged, replacem ent of axle cen ter may be n e c ­
e ssa r y . If draw key h o les becom e enlarged beyond
u se of new key, rep lace axle cen ter. IT IS NOT
1 Steering Knuckle
2 Cap Screw
3 Upper King Pin
Bearing Cap
4 King Pin Bearing Cap
Gasket
5 Lubrication Fitting
6
Shim
7 Draw Key
8
Stop Screw Lock Nut
9 Stop Screw
10 Thrust Bearing
11 Lower King Pin
Bearing Cap
12 Cap Screw
13 King Pin Bearing Cap
Gasket
14 Lower Bushing
15 O-ring Seal
16 Upper Bushing
17 King Pin
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL