Chevrolet 30 Series 1967 Service Manual page 208

REAR SUSPENSION AND DRIVE LINE 4-50
The tandem rear axle installation (fig. 91) consists of a
rearward rear axle (Eaton Model 30R) and a forward rear
axle (Eaton Model 30D) which carries a single speed
power divider with an inter-axle differential. An air or
vacuum operated shift mechanism is used to lock out the
inter-axle differential to provide positive drive to both
axles when required.
Drive is transmitted from the transmission through a
conventional propeller shaft to the power divider input
shaft (fig. 91). The input shaft supports the inter-axle
differential which transmits equal driving force to two
helical gears, one mated to a gear on the forward rear
axle pinion shaft to drive the forward axle and the other
mated to a gear on the power divider output shaft to
transmit drive force through an inter-axle propeller shaft
to the rearward axle. Both axles drive at all times, so
the inter-axle differential (3rd differential) is provided to
REARWARD REAR AXLE
The rearward axle assembly is maintained in the same
manner as outlined for the single speed Eaton rear axle.
FORWARD REAR AXLE
The power divider and inter-axle differential are part
INTER-AXLE DIFFERENTIAL
LOCK SHIFT SYSTEM
VACUUM OPERATED
Operation
The toggle switch on the center instrument panel con­
trols the warning light in the instrument cluster (fig. 93)
and the solenoid operated lock valve at the frame side
rail (fig. 94).
The solenoid, when energized, actuates the lock valve
connected between the locking cylinder, mounted at the
front of the forward rear axle, and the engine vacuum
supply (fig. 94).
The locking cylinder (fig. 95) operates the lockout shift
lever so the sliding clutch engages the input shaft helical
and differential side gear to divide power equal to both
axles.
Checking For Leakage
Place the truck on level ground with the parking brake
released and the transmission in neutral. Start the en­
gine with the control switch at "on" (the power divider
differential locked out). Accelerate the engine for a few
GENERAL DESCRIPTION
MAINTENANCE AND ADJUSTMENTS
SERVICE OPERATIONS
allow differential action between the two axles. When
extra traction is required to move the vehicle, the inter­
axle differential can be locked out so equal power can be
delivered to each axle. A toggle switch in the driver's
compartment actuates the solenoid-controlled, vacuum
operated, lock-out shift lever at the axle. The air system
is controlled by a lever operated valve in the drivers
compartment. Air pressure actuates a shift cylinder
which is mounted on the axle. Both systems move the
sliding clutch into engagement with the input shaft helical
gear. A light installed on the dash warns when differen­
tial is locked out.
NOTE:
Use lockout only in slippery going.
When differential is to be locked out, vehicle
must be completely stopped. Continuous unnec­
essary use of lockout must be avoided.
of the forward rear axle differential carrier cover as­
sembly and may be removed when the carrier is either in
or out of the vehicle. The differential, ring gear and
pinion are serviced in the same manner as outlined for
the single speed Eaton rear axle.
F ig . 93 - D ifferen tial Lock Switch and Warning Light Installation