Chevrolet 70 Series 1970, Service Manual

Page: 214 / 841

REAR SUSPENSION 4-1
SECTION 4
REAR SUSPENSION
T h is group i s divided into se c tio n s shown in the index below:
P age No.
R ear A xle and C o n t r o l s .................................................................... 4-1
R ear Springs and S u s p e n s i o n ........................................................ 4-25
R ear Hubs and B e a r in g s .................................................................... 4-63
P ro p eller S h a f t s .................................................................................. 4-67
REAR AXLE AND CONTROLS
DESCRIPTION
R ear a x le s u sed on a ll v e h ic le s covered by
th is publication are full floating type, using Hotch­
k is s , radius rod, or le a f spring drive.
Single a x le s are u su ally H otchkiss and lea f
spring d rive, while tandem un its are radius rod
d rive.
Tandem su sp en sion s are Hendrickson equaliz­
ing beam type, R eyco, C hevrolet A ir Suspension, or
P age and P age, with both a x le s driving, however,
P age and P age su sp en sion is usually u sed when
only one axle is driving in a tandem suspension.
R ear a x le s a r e Hypoid or sp ira l bevel pinion
and b evel gear type. Pinion is straddle mounted
betw een r o lle r bearing and two adjustable tapered
r o lle r b earin gs. D ifferen tial is supported by ad­
justable tapered r o lle r bearings mounted in dif­
feren tial c a r r ie r .
Housing is eith er banjo or bowl type, with
spring s e a ts and b ra ck ets, a lso brake mounting
brack ets welded to housing. T his type co n stru c­
tion p rovid es exact alignm ent and location of axle
a ssem b ly at tim e of a ssem b ly and installation.
A xle sh afts are fu ll-floatin g type. Inner end
o f shaft i s splined and engages sim ila r sp lin e s in
differential sid e gear. Outer end o f shaft is
flanged and i s attached to wheel hub by studs,
tapered dow els, and nuts.
REAR AXLE CONTROLS
Paragraphs follow ing are intended to provide
inform ation relative to sev e r a l sy ste m s u sed to
shift 2 - speed and 3 - speed a x le s. Inform ation is
a lso included on in te r -a x le d ifferential lock con­
t r o ls u sed on the forward unit of som e tandem
axle units.
TWO-SPEED ELECTRIC SHIFT
The e le c tr ic shift control sy stem c o n s is ts of
a control sw itch, speedom eter adapter, shift units,
and interconnecting w iring h arn ess.
CONTROL SWITCH
The control sw itch, mounted on tra n sm issio n
shift le v e r c o n s ists of a shift button which i s p o s i­
tioned by the driver to operate a shift unit at axle.
The d riv er s e le c t s the axle ratio by moving con­
tro l button to se le c t LOW and HIGH axle range
(fig. 1). Movement of control button com p letes
circu it to one fie ld of shift unit m otor when in
HIGH and to opposite field when in LOW.
SHIFT UNIT
The shift unit and autom atic sw itch assem b ly
i s mounted on the differential c a r r ie r (fig.
2
).
T h is unit, controlled by the control sw itch, sh ifts
the axle into LOW or HIGH range.
When the control sw itch button i s in HIGH
range, w iring c a r r ie s current to one field of the
unit m otor. The arm ature and drive scr ew turn in
a clock w ise direction and move the nut down
(fig. 3).
When the nut has traveled a sufficien t d is ­
tance to wind the torsion spring, a contact bumper
on the nut breaks an e le c tr ic a l connection on the
autom atic sw itch so that m otor is no longer
en ergized and the arm ature stop s rotating. To
make surje that the nut cannot travel back on the
screw due to vibration, a ball screw detent spring
holds the nut at the end of it s tra v el on the screw .
The nut m oves the spring winding lev er down
pivoting on winding and actuating le v e r shaft
winds the to rsio n spring for high. Thus an in­
cre a se d load i s put on the spring, and in th is
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL