GMC 4000 Series Service Manual page 132

This section is divided into three sub-sections as shown in index below:
Section
4A
4B
4C
4D
Rear axles used on all vehicles covered by
this publication are full floating type, using Hotch­
k iss or leaf spring drive.
Rear axles are Hypoid or spiral bevel pinion
gear type. Pinion is straddle mounted between
roller bearing and two adjustable tapered roller
bearings. Differential is supported by adjustable
tapered roller bearings in differential carrier.
Housing is either banjo or bowl type, with
Paragraphs following are intended to provide
information relative to several system s used to
shift 2-speed axles into high or low speeds.
ELECTRIC SHIFT
The electric shift control system consists of
a control switch, speedometer adapter, shift units,
and interconnecting wiring harness.
CONTROL SWITCH
The control switch, mounted on transmission
shift lever consists of a shift button which is posi­
tioned by the driver to operate a shift unit at axle.
The driver selects the axle ratio by moving con­
trol button (fig. 1) to select "Low" and "High" axle
range. Movement of control button completes c ir ­
cuit to one field of shift unit motor when in "High"
and to opposite field when in "Low." Refer to ap­
plicable "Wiring Diagrams" booklet.
SHIFT UNIT
The shift unit and automatic switch assembly
is mounted on differential carrier (fig. 2). This
unit, controlled by the control switch, shifts the
axle into "Low" or "High" range.
G M C S E R V I C E M A N U A L
SECTION 4
HeaA, S u A n e fiA ia n
Rear Axle and Controls
Rear S p r in g s ....................................................................
Rear Hubs and B e a r in g s ..............................................
Propeller Shafts .............................................................
SECTION 4A
Reasi A x le a*t& G osttkoii.
DESCRIPTION
REAR AXLE CONTROLS
..............................................
spring seats and brackets, also brake mounting
brackets welded to housing. This type construction
provides exact alignment and location of the axle
assembly at time of assembly and installation.
Axle shafts are full-floating type. Inner end
of shaft is splined and engages sim ilar splines in
differential side gear. Outer end of shaft is flanged
and is attached to the wheel hub by studs, tapered
dowels, and nuts.
When the control switch button is in "Hi"
range, wiring carries current to one field of the
unit motor. The armature and drive screw turn in
a clockwise direction and move the nut down (fig.3).
When the nut has traveled a sufficient distance
to wind the torsion spring, a contact bumper on the
nut breaks an electrical connection on the auto-
Sec. 4A
Page 125
Page No.
125
145
149
155