Emergency Drive - Jeep 1979 CJ-5 Technical & Service Manual

1-13
Limited slip differentia!
in Quadra-Trac transmits
engine torque to both front
and rear axles as determined
by traction available. O p t i m u m
traction is maintained, resulting
in m a x i m u m c o n t r o l .
FRONT
A X L E
Q U A D R A - T R A C
T R A N S F E R CASE
80346
Fig. 2D-18 Quadra-Trac Transfer Case
wheels is insufficient, the brake cone connecting the low
traction wheels to the differential will release momen-
tarily. This allows full torque transfer to the high-trac-
tion wheels through the opposite brake cone. Locking
action on this cone is automatically increased by differ-
ential pinion reaction. During operation, this sequence
of apply-release force on the cones occurs constantly to
compensate for the variances in tractive force at either
axle.
Because the cones will release under excessive or vari-
able torque loads, torque windup can be dissipated regu-
larly throughout normal operation. This feature permits
full-time four wheel drive at all speeds and in most
driving conditions.
Lubricant pressure buildup within the transfer case is
relieved through a vent located in the diaphragm cover.
This vent must remain open at all times to prevent loss
of lubricant from the vent or past the seals and gaskets
in the transfer case.
Emtrpiif Iriwi
Emergency Drive is a vacuum operated control sys-
tem which locks the front and rear wheel drives together
resulting in undifferentiated four wheel drive. This fea-
ture allows the vehicle to be moved from a high centered
condition, permits continued operation in two wheel
drive in the event of an axle or propeller shaft failure,
and assists in maintaining traction in soft sand or mud,
or on extremely icy surfaces.
CAUTION: Emergency Drive is provided for extreme
situations only and must not be used for normal oper-
ation. The Quadra-Trac Transfer Case is designed to
dissipate torque windup in the fully differentiated mode
only. If the vehicle is driven at normal road speeds with
Emergency Drive engaged, the transfer case could be
damaged severely. The only situations where Emer-
gency Drive should be engaged are when plowing snow
on extremely slippery surfaces, when one axle or prop-
eller shaft has malfunctioned (permits continued oper-
ation in two wheel drive), when driving on extremely icy
surfaces, when mired in soft sand or mud, or when the
vehicle has become high centered.
The Emergency Drive system is operated by engine
vacuum. System controls consist of a vacuum switch
located in the glove box, a vacuum control diaphragm
located in the transfer case front cover, interconnecting
vacuum hoses, and a plunger-type indicator switch
mounted in the transfer case front cover (figs. 2D-19,
2D-20). An indicator light mounted in the instrument
panel is used to signal the driver when Emergency Drive
is engaged. The indicator light, which is activated by the
indicator switch in the transfer case, remains illumi-
nated until Emergency Drive is disengaged.
The transfer case internal mechanical components op-
erated by the vacuum system and which effect lockup
consist of: the lockup hub shift fork, lockup hub, and
differential case rear end cap. The shift fork is located
on the control diaphragm piston by two retaining rings.
The fork engages in a groove machined in the lockup hub
and the hub is splined to the rear output shaft.
Emergency Drive Operation
When the glove box switch is turned to Emergency
Drive position, the switch allows engine vacuum to enter
'the apply side of the control diaphragm. As the apply